19) HISTORY OF COMPUTER 'S PERIPHERAL DEVICES

by engr. AFAN BAHADUR KHAN



This category focuses on the history and timeline of various items used in computers, Each item is explained in general, providing information suitable for everyone from beginners to advanced users.
Take a cruise through history to discover some of the key developments that have brought us to our present state of computing, including the development of numbers, the introduction of mechanical aids to calculation, the evolution of electronics, and the impact of electronics on computing.
No one person may be credited with the invention of computers, but several names stand proud in the crowd. The following offers some of the more notable developments and individuals, with great regret for any omissions.


1- CR- ROMS




CD-R is an abbreviation of compact disc recordable. Operating on the same premise as a CD, a CD-R is thin disc made of polycarbonate with 120mm diameter used to store music or data. However, unlike conventional CD media, a CD-R has dye core instead of a metal core. A laser is used to etch "pits" into the dye so that the disc can later be read by the laser in a CD-ROM drive or CD player. Once used, a CD-R cannot be erased and reused, but it can be recorded in multiple sessions by using UDF format. A cdrw, though, can be reused.
There was some incompatability with CD-R and older CD-ROM drives. This was primarily due to the lower reflectivity of the CD-R disc. In general, CD drives marked as 8x or greater will usually read CD-R discs.


2- DVD ROMS




DVD started as the Digital Video Disc but now means Digital Versatile Disc or just DVD. It is a multi-application family of optical disc formats for read-only, recordable and re-writable applications. The main features of the DVD formats are:
Backwards compatibility with current CD media. All DVD hardware will play audio CDs and CD-ROMs (although not all hardware will play CD-Rs or CD-RWs).
Physical dimensions identical to compact disc but using two 0.6 mm thick substrates, bonded together.
Single-layer/dual-layer and single/double sided options.
Up to 4.7 GB read-only capacity per layer, 8.5 GB per side maximum.
Designed from the outset for video, audio and multimedia, not just audio.
All formats use a common file system (UDF).
Digital and analogue copy protection for DVD-Video and DVD-Audio built into standard.
Recordable and re-writable versions are part of the family.
DVD started in 1994 as two competing formats, Super Disc (SD) and Multimedia CD (MMCD). DVD now is the result of an agreement by both camps on a single standard to meet the requirements of all the various industries involved.


3- FLOPPY DISKETTES




In 1971, an IBM team led by Alan Shugart invented the 8-inch floppy diskette. This floppy was an 8" plastic disk coated with magnetic iron oxide; data was written to and read from the disk's surface. The nickname "floppy" came from it's flexibility. The floppies were considered revolutionary devices at the time for its portability which provided a new and easy physical means of transporting data from one computer to another.
A floppy disk is a circle of magnetic material similar to any kind of recording tape; one or two sides of the disk are used for recording. The disk drive grabs the floppy by its center and spins it like a record inside its housing. The read/write head, much like the head on a tape deck, contacts the surface through an opening in the plastic shell, or envelope.


4- HARD DISK DRIVES


The hard disk drive has short and fascinating history. In 24 years it evolved from a monstrosity with fifty, two foot diameter disks holding five MBytes (5,000 bytes) of data to today's drives measuring 3 /12 inches wide and an inch high (and smaller) holding more than 70 GBytes (70,000,000,000 bytes/characters). Here, then, is the short history of this marvelous device.
Before the disk drive there were drums... In 1950 Engineering Research Associates of Minneapolis built the first commercial magnetic drum storage unit for the U.S. Navy, the ERA 110. It could store one million bits of data and retrieve a word in 5 thousandths of a second.
In 1956 IBM invented the first computer disk storage system, the 305 RAMAC (Random Access Method of Accounting and Control). This system could store five MBytes. It had fifty, 24-inch diameter disks!
By 1961 IBM had invented the first disk drive with air bearing heads and in 1963 they introduced the removable disk pack drive. In 1970 the eight inch floppy disk drive was introduced by IBM. My first floppy drives were made by Shugart who was one of the "dirty dozen" who left IBM to start their own companies. In 1981 two Shugart 8 inch floppy drives with enclosure and power supply cost me about $350.00. They were for my second computer. My first computer had no drives at all.
In 1973 IBM shipped the model 3340 Winchester sealed hard disk drive, the predecessor of all current hard disk drives. The 3340 had two spindles each with a capacity of 30 MBytes, and the term "30/30 Winchester" was thus coined.
Seagate ST4053 40 MByte 5 1/4 inch, full-height "clunker" with ST506 interface and voice coil circa 1987. My cost was $435.00. In 1980, Seagate Technology introduced the first hard disk drive for microcomputers, the ST506. It was a full height (twice as high as most current 5 1/4" drives) 5 1/4" drive, with a stepper motor, and held 5 Mbytes. My first hard disk drive was an ST506. I cannot remember exactly how much it cost, but it plus its enclosure, etc. was well over a thousand dollars. It took me three years to fill the drive. Also, in 1980 Phillips introduced the first optical laser drive. In the early 80's, the first 5 1/4" hard disks with voice coil actuators (more on this later) started shipping in volume, but stepper motor drives continued in production into the early 1990's. In 1981, Sony shipped the first 3 1/2" floppy drives.
In 1983 Rodime made the first 3.5 inch rigid disk drive. The first CD-ROM drives were shipped in 1984, and "Grolier's Electronic Encyclopedia," followed in 1985. The 3 1/2" IDE drive started it's existence as a drive on a plug-in expansion board, or "hard card." The hard card included the drive on the controller which, in turn, evolved into Integrated Device Electronics (IDE) hard disk drive, where the controller became incorporated into the printed circuit on the bottom of the hard disk drive. Quantum made the first hard card in 1985.
In 1986 the first 3 /12" hard disks with voice coil actuators were introduced by Conner in volume, but half (1.6") and full height 5 1/4" drives persisted for several years. In 1988 Conner introduced the first one inch high 3 1/2" hard disk drives. In the same year PrairieTek shipped the first 2 1/2" hard disks.
In 1997 Seagate introduced the first 7,200 RPM, Ultra ATA hard disk drive for desktop computers and in February of this year they introduced the first 15,000 RPM hard disk drive, the Cheetah X15. Milestones for IDE DMA, ATA/33, and ATA/66 drives follow: 1994 DMA, Mode 2 at 16.6 MB/s -- 1997 Ultra ATA/33 at 33.3 MB/s -- 1999 Ultra ATA/66 at 66.6 MB/s



5- IDE ( INTELLIGENT DRIVER ELECTRONICS)


Compaq started the development of the IDE interface. This standard was designed specially for the IBM PC and can achieve high data transfer rates through a 1:1 interleave factor and caching by the actual disk controller - the bottleneck is often the old AT bus and the drive may read data far quicker than the bus can accept it, so the cache is used as a buffer. Theoretically 1MBps is possible but 700KBps is perhaps more typical of such drives. This standard has been adopted by many other models of computer, such the Acorn Archimedes A4000 and above. A later improvement was EIDE, laid down in 1989, which also removed the maximum drive size of 528MB and increased data transfer rates.


6- MODEMs




Modem, device that converts between analog and digital signals. Digital signals, which are used by computers, are made up of separate units, usually represented by a series of 1's and 0's. Analog signals vary continuously; an example of an analog signal is a sound wave. Modems are often used to enable computers to communicate with each other across telephone lines. A modem converts the digital signals of the sending computer to analog signals that can be transmitted through telephone lines. When the signal reaches its destination, another modem reconstructs the original digital signal, which is processed by the receiving computer. If both modems can transmit data to each other simultaneously, the modems are operating in full duplex mode; if only one modem can transmit at a time, the modems are operating in half duplex mode.
To convert a digital signal to an analog one, the modem generates a carrier wave and modulates it according to the digital signal. The kind of modulation used depends on the application and the speed of operation for which the modem is designed. For example, many high-speed modems use a combination of amplitude modulation, where the amplitude of the carrier wave is changed to encode the digital information, and phase modulation, where the phase of the carrier wave is changed to encode the digital information. The process of receiving the analog signal and converting it back to a digital signal is called demodulation. The word "modem" is a contraction of its two basic functions: modulation and demodulation.
Dennis C. Hayes invented the PC modem in 1977, establishing the critical technology that allowed today's online and Internet industries to emerge and grow. He sold the first Hayes modem products to computer hobbyists in April of 1977 and founded D.C. Hayes Associates, Inc., the company known today as Hayes Corp., in January of 1978. Hayes quality and innovation resulted in performance enhancements and cost reductions that led the industry in the conversion from leased line modems to intelligent dial modems - the PC Modem.
Hayes-Compatible, in computer science, an adjective used to describe a modem that responds to the same set of commands as a modem manufactured by Hayes Microcomputer Products, originators of the de facto standard for microcomputer modems.



7- MONITORS






Often referred to as a monitor when packaged in a separate case, the display is the most-used output device on a computer. The display provides instant feedback by showing your text and graphic images as you work or play. Most desktop displays use a cathode ray tube (CRT), while portable computing devices such as laptops incorporate liquid crystal display (LCD), light-emitting diode (LED), gas plasma or other image projection technology. Because of their slimmer design and smaller energy consumption, monitors using LCD technologies are beginning to replace the venerable CRT on many desktops.
Displays have come a long way since the blinking green monitors in text-based computer systems of the 1970s. Just look at the advances made by IBM over the course of a decade: In 1981, IBM introduced the Color Graphics Adapter (CGA), which was capable of rendering four colors, and had a maximum resolution of 320 pixels horizontally by 200 pixels vertically. IBM introduced the Enhanced Graphics Adapter (EGA) display in 1984. EGA allowed up to 16 different colors and increased the resolution to 640x350 pixels, improving the appearance of the display and making it easier to read text. In 1987, IBM introduced the Video Graphics Array (VGA) display system. Most computers today support the VGA standard and many VGA monitors are still in use. IBM introduced the Extended Graphics Array (XGA) display in 1990, offering 800x600 pixel resolution in true color(16.8 million colors) and 1,024x768 resolution in 65,536 colors. Most displays sold today support the Ultra Extended Graphics Array (UXGA) standard. UXGA can support palette of up to 16.8 million colors and resolutions of up to 1600x1200 pixels, depending on the video memory of the graphics card in your computer. The maximum resolution normally depends on the number of colors displayed. For example, your card might require that you choose between 16.8 million colors at 800x600, or 65,536 colors at 1600x1200.
The combination of the display modes supported by your graphics adapter and the color capability of your monitor determine how many colors can be displayed. For example, a display that can operate in SuperVGA (SVGA) mode can display up to 16,777,216 (usually rounded to 16.8 million) colors because it can process a 24-bit-long description of a pixel. The number of bits used to describe a pixel is known as its bit depth. With a 24-bit bit depth, 8 bits are dedicated to each of the three additive primary colors -- red, green and blue. This bit depth is also called true color because it can produce the 10,000,000 colors discernible to the human eye, while a 16-bit display is only capable of produ cing 65,536 colors. Displays jumped from 16-bit color to 24-bit color because working in 8-bit increments makes things a whole lot easier for developers and programmers.
Briefly, the measure of how much space there is between a display's pixels. When considering dot pitch, remember that smaller is better. Packing the pixels closer together is fundamental to achieving higher resolutions. A display normally can support resolutions that match the physical dot (pixel) size as well as several lesser resolutions. For example, a display with a physical grid of 1280 rows by 1024 columns can obviously support a maximum resolution of 1280x1024 pixels. It usually also supports lower resolutions such as 1024x768, 800x600, and 640x480.
In monitors based on CRT technology, the refresh rate is the number of times that the image on the display is drawn each second. If your CRT monitor has a refresh rate of 72 Hertz (Hz), then it cycles through all the pixels from top to bottom 72 times a second. Refresh rates are very important because they control flicker, and you want the refresh rate as high as possible. Too few cycles per second and you will notice a flickering, which can lead to headaches and eye strain.


8- MOUSE POINTERS




Years before personal computers and desktop information processing became commonplace or even practicable, Douglas Engelbart had invented a number of interactive, user-friendly information access systems that we take for granted today: the computer mouse was one of his inventions. At the Fall Joint Computer Conference in San Francisco in 1968, Engelbart astonished his colleagues by demonstrating the aforementioned systems---using an utterly primitive 192 kilobyte mainframe computer located 25 miles away! Engelbart has earned nearly two dozen patents, the most memorable being perhaps for his "X-Y Position Indicator for a Display System": the prototype of the computer "mouse" whose convenience has revolutionized personal computing.
Mouse (computer), a common pointing device, popularized by its inclusion as standard equipment with the Apple Macintosh. With the rise in popularity of graphical user interfaces in MS-DOS; UNIX, and OS/2, use of mice is growing throughout the personal computer and workstation worlds. The basic features of a mouse are a casing with a flat bottom, designed to be gripped by one hand; one or more buttons on the top; a multidirectional detection device (usually a ball) on the bottom; and a cable connecting the mouse to the computer. By moving the mouse on a surface (such as a desk), the user typically controls an on-screen cursor. A mouse is a relative pointing device because there are no defined limits to the mouse's movement and because its placement on a surface does not map directly to a specific screen location. To select items or choose commands on the screen, the user presses one of the mouse's buttons, producing a "mouse click."
Mouse Patent # 3,541,541 issued 11/17/70 for X-Y Position Indicator For A Display System Douglas Engelbart's patent for the mouse is only a representation of his pioneering work in the design of modern interactive computer environments.



9- PLOTTERS


A plotter is a vector graphics printing device that connects to a computer.
Plotters print their output by moving a pen across the surface of a piece of paper. This means that plotters are restricted to line art, rather than raster graphics as with other printers. They can draw complex line art, including text, but do so very slowly because of the mechanical movement of the pens.
Another difference between plotters and printers is that a printer is aimed primarily at printing text. This makes it fairly easy to control, simply sending the text to the printer is usually enough to generate a page of output. This is not the case of the line art on a plotter, where a number of printer control languages were created to send the more detailed information like "draw a line from here to here". The most popular of these is likely HPGL.
Early plotters were created by attaching ball-point pens to drafting pantographs and driving the machines with motors controlled by the computer. This had the disadvantage of being somewhat slow to move, as well as requiring floor space equal to the size of the paper. Later versions worked by placing the paper over a roller which moved the paper back and forth for X motion, while the pen moved back and forth on a single arm for Y motion. Another change was the addition of an elecrtically controlled clamp to hold the pens, which allowed them to be changed and thus create multi-colored output.
For a time in the 1980's smaller "home-use" plotters became popular for experimentation in computer graphics. But their low speed meant they were not useful for general printing purposes, and you would need another conventional printer for those jobs. With the widespread availability of high-resolution inkjets and laser printers, plotters have all but disappeared.
Plotters are used primarily in drafting and CAD applications, where they have the advantage of working on very large paper sizes while maintaining high resolution. Another use has been found by replacing the pen with a cutter, and in this form plotters can be found in many garment and sign shops.


10- SOUND CARDS





Computers were never designed to handle sound. About the only audio you'd hear from an early computer were beeps, designed to tell you if there was a problem. Computer games manipulated these beeps, to produce truly awful music as an accompaniment to games like Space Invaders. However, surely there was more to sounds than beeps? Thankfully a company from the Far East recognised this, and made the original Sound Blaster sound card for the now ancient ISA bus. It could record real audio and play it back, something of a quantum leap. It also had a MIDI interface, still common on sound cards today, which could control synthesisers, samplers and other electronic music equipment. It could "create" sounds by using FM synthesis, which were not that realistic but were nevertheless better than simple beeps. The quality of the audio was 8 bit 11 kHz, so sounded roughly like an AM radio.
The sound card is quite a complicated piece of electronics. The most important parts are the ADC and DAC. The ADC (Analogue-to-Digital convertor) takes in analogue signals, for example from a microphone and converts them to digital signals for the computer to store. The DAC (Digital-to-Analogue convertor) does the opposite. However, in the future there will be no need for either, since both speakers and microphones will be able to directly record and playback digital signals directly. The heart of a CD player is also the DAC. CD players tend to sound better than the average, because they generally cost more and are simpler devices. Hence the DAC component of a CD player tends to be more expensive (and thus better quality). Having said that, the quality of DACs on sound cards is improving all the time.
The advantage of digital audio (ie. storing audio as 1s and 0s) is that no matter how many times it is copied it remains identical, and does not degrade like analogue sources, such as vinyl. The next major development for sound cards was the leap up to 16 bit 44.1 kHz stereo audio, ie. CD quality. However, this posed problems for the archaeic ISA bus, which had problems playing back and recording more than one track at the same time. This effectively meant it was difficult to use your computer to make phone calls on the internet (since you couldn't talk and hear at the same time!) or use it as a multitrack audio editor (for musicians). The PCI bus solved this problem. Nowadays virtually all soundcards are PCI. Currently we are seeing 24 bit 96 kHz sound cards emerging, which promise even better sound quality than CDs! Some sound cards also decode Dolby Digital sound, so you can connect computer speakers to them for surround sound, when playing back DVDs. High-end sound cards also come with digital inputs and outputs, letting you bypass the sound cards convertors and use external ones.
Recently there has been the advent of the USB and Firewire buses. These enable you to connect fast external devices to your computer. Sound cards attached to the USB bus cannot playback as many tracks simultaneously as a PCI sound card. However, for people other than musicans this is hardly relevant. Also being external they can be used on more than one machine and on laptops, which notoriously have poor sound cards. There are also several external Firewire sound cards. These are quite expensive and designed to playback and record many tracks. Consequently they are a waste of money if all you do is watch DVDs or play MP3s on your computer.
Sound on the PC has come a long way since all those beeps twenty years ago!


11- TOUCH SCREENS


A touch screen is a special type of visual display unit with a screen which is sensitive to pressure or touching. The screen can detect the position of the point of touch. The design of touch screens is best for inputting simple choices and the choices are programmable. The device is very user-friendly since it 'talks' with the user when the user is picking up choices on the screen.
Touch technology turns a CRT, flat panel display or flat surface into a dynamic data entry device that replaces both the keyboard and mouse. In addition to eliminating these separate data entry devices, touch offers an "intuitive" interface. In public kiosks, for example, users receive no more instruction than 'touch your selection.'
Specific areas of the screen are defined as "buttons" that the operator selects simply by touching them. One significant advantage to touch screen applications is that each screen can be customized to reflect only the valid options for each phase of an operation, greatly reducing the frustration of hunting for the right key or function.
Pen-based systems, such as the Palm Pilot® and signature capture systems, also use touch technology but are not included in this article. The essential difference is that the pressure levels are set higher for pen-based systems than for touch.
Touch screens come in a wide range of options, from full color VGA and SVGA monitors designed for highly graphic Windows® or Macintosh® applications to small monochrome displays designed for keypad replacement and enhancement.
Specific figures on the growth of touch screen technology are hard to come by, but a 1995 study last year by Venture Development Corporation predicted overall growth of 17%, with at least 10% in the industrial sector.
According to Jim Sido, IBM's National Marketing Manager for Food Service Products, this year should see even greater growth than last year.
John Muhlberger, Director of Product Management at PAR Microsystems estimated that, for POS applications, touch screen terminals outsell keyboard terminals about 4:1, even though the touch terminals cost somewhat more.
Other vendors agree that touch screen technology is becoming more popular because of its ease-of-use, proven reliability, expanded functionality, and decreasing cost.

18) HISTORY OF PRINTING

by engr. AFAN BAHADUR KHAN



The history of printing began as an attempt to make easier and reduce the cost of reproducing multiple copies of documents, fabrics, wall papers and so on. Printing streamlined the process of communication, and contributed to the development of commerce, law, religion and culture.



1- WOODBLOCK PRINTING



Woodblock printing is a technique for printing text, images or patterns used widely throughout East Asia and originating in China in antiquity as a method of printing on textiles and later paper. As a method of printing on cloth, the earliest surviving examples from China date to before 220, and from Egypt to the 4th century. Ukiyo-e is the best known type of Japanese woodblock art print. Most European uses of the technique on paper are covered by the art term woodcut, except for the block-books produced mainly in the fifteenth century.




Yuan Dynasty woodblock edition of a Chinese play





The use of round "cylinder seals" for rolling an impress onto clay tablets goes back to early Mesopotamian civilization before 3,000 BCE, where they are the most common works of art to survive, and feature complex and beautiful images. In both China and Egypt, the use of small stamps for seals preceded the use of larger blocks. In Egypt, Europe and India, the printing of cloth certainly preceded the printing of paper or papyrus; this was probably also the case in China. The process is essentially the same - in Europe special presentation impressions of prints were often printed on silk until at least the seventeenth century.



1.1- In China



The earliest woodblock printed fragments to survive are from China and are of silk printed with flowers in three colours from the Han dynasty (before 220 CE). The earliest Egyptian printed cloth dates from the 4th century.

It is clear that the Chinese were the first by several centuries to use the process to print solid text, and equally that, much later, in Europe the printing of images on cloth developed into the printing of images on paper (woodcuts). It is also now established that the use in Europe of the same process to print substantial amounts of text together with images in block-books only came after the development of movable type in the 1450s.


1.2- In the Islamic world



Block printing, called tarsh in Arabic was developed in Arabic Egypt during the 9th-10th centuries, mostly for prayers and amulets. It is unclear whether the print blocks were made from metal or wood or other materials. This technique, however, appears to have had very little influence outside of the Muslim world. Though Europe adopted woodblock printing from the Muslim world, initially for fabric, the technique of metal block printing was also unknown in Europe. Block printing later went out of use in Islamic Central Asia after movable type printing was introduced from China.


1.3- In Europe


Block printing first came to Christian Europe as a method for printing on cloth, where it was common by 1300. Images printed on cloth for religious purposes could be quite large and elaborate, and when paper became relatively easily available, around 1400, the medium transferred very quickly to small woodcut religious images and playing cards printed on paper. These prints were produced in very large numbers from about 1425 onwards.

Around the mid-century, block-books, woodcut books with both text and images, usually carved in the same block, emerged as a cheaper alternative to manuscripts and books printed with movable type. These were all short heavily illustrated works, the bestsellers of the day, repeated in many different block-book versions: the Ars moriendi and the Biblia pauperum were the most common. There is still some controversy among scholars as to whether their introduction preceded or, the majority view, followed the introduction of movable type, with the range of estimated dates being between about 1440–1460.

The volume of Joseph Needham's Science and Civilization in China dealing with Paper and printing has a chapter that suggests that "European block printers must not only have seen Chinese samples, but perhaps had been taught by missionaries or others who had learned these un-European methods from Chinese printers during their residence in China.", but he also admitted that the "only evidence of European printing transmitted from China is a lack of counterevidence". However, paper itself was needed for the printing process and this came to Europe via trade with the Arabs from China. Historians acknowledge that paper indeed came from China without which printing would have been impossible, however, there is less direct evidence of the influence of printing technology from Asia and its influence on European printing technology.


2- STENCIL



Stencils may have been used to color cloth for a very long time; the technique probably reached its peak of sophistication in Katazome and other techniques used on silks for clothes during the Edo period in Japan. In Europe, from about 1450 they were very commonly used to colour old master prints printed in black and white, usually woodcuts. This was especially the case with playing-cards, which continued to be coloured by stencil long after most other subjects for prints were left in black and white. Stenciling back in the 2600 BC's was different. They used color from plants and flowers such as indigo (which extracts blue). Stencils were used for mass publications, as the type didn't have to be hand-written.


3- MOVABLE TYPE


Movable type is the system of printing and typography using movable pieces of metal type, made by casting from matrices struck by letterpunches.

Around 1040, the first known movable type system was created in China by Bi Sheng out of porcelain. Metal movable type was first invented in Korea during the Goryeo Dynasty (around 1230). Neither movable type system was widely used, one reason being the enormous Chinese character set.




A case of cast metal type pieces and typeset matter in a composing stick



It is traditionally summarized that Johannes Gutenberg, of the German city of Mainz, developed European movable type printing technology around 1439 and in just over a decade, the European age of printing began. However, the details show a more complex evolutionary process spread over multiple locations. Also, Johann Fust and Peter Schöffer experimented with Gutenberg in Mainz.

Compared to woodblock printing, movable type page-setting was quicker and more durable. The metal type pieces were more durable and the lettering was more uniform, leading to typography and fonts. The high quality and relatively low price of the Gutenberg Bible (1455) established the superiority of movable type, and printing presses rapidly spread across Europe, leading up to the Renaissance, and later all around the world. Today, practically all movable type printing ultimately derives from Gutenberg's movable type printing, which is often regarded as the most important invention of the second millennium.

Gutenberg is also credited with the introduction of an oil-based ink which was more durable than previously used water-based inks. Having worked as a professional goldsmith, Gutenberg made skillful use of the knowledge of metals he had learned as a craftsman. Gutenberg was also the first to make his type from an alloy of lead, tin, and antimony, known as type metal, printer's lead, or printer's metal, which was critical for producing durable type that produced high-quality printed books, and proved to be more suitable for printing than the clay, wooden or bronze types used in East Asia. To create these lead types, Gutenberg used what some considered his most ingenious invention, a special matrix wherewith the moulding of new movable types with an unprecedented precision at short notice became feasible. Within a year of printing the Gutenberg Bible, Gutenberg also published the first coloured prints.

The invention of the printing press revolutionized communication and book production leading to the spread of knowledge. Rapidly, printing spread from Germany by emigrating German printers, but also by foreign apprentices returning home. A printing press was built in Venice in 1469, and by 1500 the city had 417 printers. In 1470 Johann Heynlin set up a printing press in Paris. In 1473 Kasper Straube published the Almanach cracoviense ad annum 1474 in Kraków. Dirk Martens set up a printing press in Aalst (Flanders) in 1473. He printed a book about the two lovers of Enea Piccolomini who became pope Pius II.In 1476 a printing press was set up in England by William Caxton. Belarusian Francysk Skaryna printed the first book in Slavic language on August 6, 1517. The Italian Juan Pablos set up an imported press in Mexico City in 1539. The first printing press in Southeast Asia was set up in the Philippines by the Spanish in 1593. Stephen Day was the first to build a printing press in North America at Massachusetts Bay in 1638, and helped establish the Cambridge Press.

The Gutenberg press was much more efficient than manual copying and still was largely unchanged in the eras of John Baskerville and Giambattista Bodoni, over 300 years later. By 1800, Lord Stanhope had constructed a press completely from cast iron, reducing the force required by 90% while doubling the size of the printed area. While Stanhope's "mechanical theory" had improved the efficiency of the press, it still was only capable of 250 sheets per hour. German printer Friedrich Koenig would be the first to design a non-manpowered machine—using steam. Having moved to London in 1804, Koenig soon met Thomas Bensley and secured financial support for his project in 1807. Patented in 1810, Koenig had designed a steam press "much like a hand press connected to a steam engine." The first production trial of this model occurred in April 1811.



3.1- Flat-bed printing press



A printing press is a mechanical device for applying pressure to an inked surface resting upon a medium (such as paper or cloth), thereby transferring an image. The systems involved were first assembled in Germany by the goldsmith Johann Gutenberg in the mid-15th century. Printing methods based on Gutenberg's printing press spread rapidly throughout first Europe and then the rest of the world, replacing most block printing and making it the sole progenitor of modern movable type printing. As a method of creating reproductions for mass consumption, The printing press has been superseded by the advent of offset printing.



Printing press from 1811, photographed in Munich, Germany



Johannes Gutenberg's work in the printing press began in approximately 1436 when he partnered with Andreas Dritzehen—a man he had previously instructed in gem-cutting—and Andreas Heilmann, owner of a paper mill. It was not until a 1439 lawsuit against Gutenberg that official record exists; witnesses testimony discussed type, an inventory of metals (including lead) and his type mold.

Others in Europe were developing movable type at this time, including goldsmith Procopius Waldfoghel of France and Laurens Janszoon Coster of the Netherlands. They are not known to have contributed specific advances to the printing press. While the Encyclopædia Britannica Eleventh Edition had attributed the invention of the printing press to Coster, the company now states that is incorrect.



4- PRINTING HOUSES



Early printing houses (near the time of Gutenberg) were run by "master printers." These printers owned shops, selected and edited manuscripts, determined the sizes of print runs, sold the works they produced, raised capital and organized distribution. Some master printing houses, like that of Aldus Manutius, became the cultural centre for literati such as Erasmus.

Print shop apprentices: Apprentices, usually between the ages of 15 and 20, worked for master printers. Apprentices were not required to be literate, and literacy rates at the time were very low, in comparison to today. Apprentices prepared ink, dampened sheets of paper, and assisted at the press. An apprentice who wished to learn to become a compositor had to learn Latin and spend time under the supervision of a journeyman.
Journeyman printers: After completing their apprenticeships, journeyman (so called from the French "journée" for day) printers were free to move employers. This facilitated the spread of printing to areas that were less print-centred.

Compositors: Those who set the type for printing.

Pressmen: the person who worked the press. This was physically labour intensive.

The earliest-known image of a European, Gutenberg-style print shop is the Dance of Death by Matthias Huss, at Lyon, 1499. This image depicts a compositor standing at a compositor's case being grabbed by a skeleton. The case is raised to facilitate his work. The image also shows a pressman being grabbed by a skeleton. At the right of the printing house a bookshop is shown.



4.1- Financial aspects



Court records from the city of Mainz document that Johannes Fust was, for some time, Gutenberg's financial backer.

By the sixteenth century jobs associated with printing were becoming increasingly specialized. Structures supporting publishers were more and more complex, leading to this division of labour. In Europe between 1500 and 1700 the role of the Master Printer was dying out and giving way to the bookseller—publisher. Printing during this period had a stronger commercial imperative than previously. Risks associated with the industry however were substantial, although dependent on the nature of the publication.

Bookseller publishers negotiated at trade fairs and at print shops. Jobbing work appeared in which printers did menial tasks in the beginning of their careers to support themselves.

1500–1700: Publishers developed several new methods of funding projects.

1.Cooperative associations/publication syndicates—a number of individuals shared the risks associated with printing and shared in the profit. This was pioneered by the French.


2.Subscription publishing—pioneered by the English in the early 17th century. A prospectus for a publication was drawn up by a publisher to raise funding. The prospectus was given to potential buyers who signed up for a copy. If there were not enough subscriptions the publication did not go ahead. Lists of subscribers were included in the books as endorsements. If enough people subscribed a reprint might occur. Some authors used subscription publication to bypass the publisher entirely.


3.Installment publishing—books were issued in parts until a complete book had been issued. This was not necessarily done with a fixed time period. It was an effective method of spreading cost over a period of time. It also allowed earlier returns on investment to help cover production costs of subsequent installments.
The Mechanick Exercises, by Joseph Moxon, in London, 1683, was said to be the first publication done in installments.

Publishing trade organizations allowed publishers to organize business concerns collectively. Systems of self-regulation occurred in these arrangements. For example, if one publisher did something to irritate other publishers he would be controlled by peer pressure. Such systems are known as cartels, and are in most countries now considered to be in restraint of trade. These arrangements helped deal with labour unrest among journeymen, who faced difficult working conditions. Brotherhoods predated unions, without the formal regulations now associated with unions.



5- ROTARY PRINTING PRESS


A rotary printing press is a printing press in which the impressions are curved around a cylinder so that the printing can be done on long continuous rolls of paper, cardboard, plastic, or a large number of other substrates. Rotary drum printing was invented by Richard March Hoe in 1847, and then significantly improved by William Bullock in 1863.


6- INTAGLIO




Intaglio (pronounced in-TAL-yo) is a family of printmaking techniques in which the image is incised into a surface, known as the matrix or plate. Normally, copper or zinc plates are used as a surface, and the incisions are created by etching, engraving, drypoint, aquatint or mezzotint. Collographs may also be printed as intaglio plates. To print an intaglio plate the surface is covered in thick ink and then rubbed with tarlatan cloth to remove most of the excess. The final smooth wipe is usually done by hand, sometimes with the aid of newspaper or old public phone book pages, leaving ink only in the incisions. A damp piece of paper is placed on top and the plate and paper are run through a printing press that, through pressure, transfers the ink from the recesses of the plate to the paper.


7- LITHOGRAPHY ( 1796)




Invented by Bavarian author Aloys Senefelder in 1796, lithography is a method for printing on a smooth surface. Lithography is a printing process that uses chemical processes to create an image. For instance, the positive part of an image would be a hydrophobic chemical, while the negative image would be water. Thus, when the plate is introduced to a compatible ink and water mixture, the ink will adhere to the positive image and the water will clean the negative image. This allows for a relatively flat print plate which allows for much longer runs than the older physical methods of imaging (e.g., embossing or engraving).




An example of a 19th century lithograph depicting royal Afghan soldiers of the Durrani Empire in Afghanistan



8- CHROMOLITHOGRAPHY




Chromolithography was the first method for making true multi-color prints. Earlier attempts at polychromed printing relied on hand-coloring. The type of color printing stemmed from the process of lithography, and it includes all types of lithography that are printed in color. It replaced coloring prints by hand, and eventually served as a replica of a real painting. Lithographers sought to find a way to print on flat surfaces with the use of chemicals instead of relief or intaglio printing. Depending on the amount of colors present, a chromolithograph could take months to produce. To make what was once referred to as a “’chromo’”, a lithographer, with a finished painting in front of him, gradually built and corrected the print to look as much as possible like the painting in front of him, sometimes using dozens of layers. The process can be very time consuming and cumbersome contingent upon the skill of the lithographer.




1872 chromolithograph of roadside inn, published in Maryland


The technique for using color in printing was invented in 1796 in Germany. Considering the fact that it stemmed from lithography, there have been debates over whether chromolithography was created by Alois Senefelder, the same person who came up with printing by way of lithography. Senefelder introduced colored lithography in his 1818 Vollstaendiges Lehrbuch der Steindruckerey (A Complete Course of Lithography), and in the work, Senefelder told of his plans to print using color and he also explained the colors he wished to be able to print someday. Although Senefelder recorded ideas on chromolithography, it turns out that other countries besides Germany, such as France and England, were also heavily involved in trying to find a new way to print in color. Godefroy Engelmann of Mulhouse proved to be one of the few searching for ways to produce colored printed images when he was awarded his patent on chromolithography in July 1837. Even after Engelmann received his award, disputes over whether chromolithography was already being used continued to rise. Some sources point to the idea that chromolithography was already being used in areas of printing such as the production of playing cards.


9- OFFSET PRESS ( 1870s)



Offset printing is a widely used printing technique where the inked image is transferred (or "offset") from a plate to a rubber blanket, then to the printing surface. When used in combination with the lithographic process, which is based on the repulsion of oil and water, the offset technique employs a flat (planographic) image carrier on which the image to be printed obtains ink from ink rollers, while the non-printing area attracts a film of water, keeping the non-printing areas ink-free.


10- SCREEN PRINTING (1907)



Screenprinting has its origins in simple stencilling, most notably of the Japanese form (katazome), used who cut banana leaves and inserted ink through the design holes on textiles, mostly for clothing. This was taken up in France. The modern screenprinting process originated from patents taken out by Samuel Simon in 1907 in England. This idea was then adopted in San Francisco, California, by John Pilsworth in 1914 who used screenprinting to form multicolor prints in a subtractive mode, differing from screenprinting as it is done today.


11- FLEXOGRAPHY






Flexography (also called surface printing), often abbreviated to flexo, is a method of printing most commonly used for packaging (Labels, Tape, Bags, Boxes, Banners, Etc).



A flexo print is achieved by creating a mirrored master of the required image as a 3D relief in a rubber or polymer material. A measured amount of ink is deposited upon the surface of the printing plate (or printing cylinder) using an anilox roll. The print surface then rotates, contacting the print material which transfers the ink.

Originally flexo printing was basic in quality. Labels requiring high quality have generally been printed Offset until recently. In the last few years great advances have been made to the quality of flexo printing presses.

The greatest advances though have been in the area of PhotoPolymer Printing Plates, including improvements to the plate material and the method of plate creation. —usually photographic exposure followed by chemical etch, though also by direct laser engraving.


12- PHOTOCOPIER ( 1960s)





Xerographic office photocopying was introduced by Xerox in the 1960s, and over the following 20 years it gradually replaced copies made by Verifax, Photostat, carbon paper, mimeograph machines, and other duplicating machines. The prevalence of its use is one of the factors that prevented the development of the paperless office heralded early in the digital revolution.



13- THERMAL PRINTER


A thermal printer (or direct thermal printer) produces a printed image by selectively heating coated thermochromic paper, or thermal paper as it is commonly known, when the paper passes over the thermal print head. The coating turns black in the areas where it is heated, producing an image.


14- LASER PRINTER ( 1969)


The laser printer, based on a modified xerographic copier, was invented at Xerox in 1969 by researcher Gary Starkweather, who had a fully functional networked printer system working by 1971. Laser printing eventually became a multibillion-dollar business for Xerox.

The first commercial implementation of a laser printer was the IBM model 3800 in 1976, used for high-volume printing of documents such as invoices and mailing labels. It is often cited as "taking up a whole room," implying that it was a primitive version of the later familiar device used with a personal computer. While large, it was designed for an entirely different purpose. Many 3800s are still in use.

The first laser printer designed for use with an individual computer was released with the Xerox Star 8010 in 1981. Although it was innovative, the Star was an expensive ($17,000) system that was only purchased by a small number of laboratories and institutions. After personal computers became more widespread, the first laser printer intended for a mass market was the HP LaserJet 8ppm, released in 1984, using a Canon engine controlled by HP software. The HP LaserJet printer was quickly followed by other laser printers from Brother Industries, IBM, and others.

Most noteworthy was the role the laser printer played in popularizing desktop publishing with the introduction of the Apple LaserWriter for the Apple Macintosh, along with Aldus PageMaker software, in 1985. With these products, users could create documents that would previously have required professional typesetting.



15- DOT MATRIX PRINTER ( 1970)



A dot matrix printer or impact matrix printer refers to a type of computer printer with a print head that runs back and forth on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like a typewriter. Unlike a typewriter or daisy wheel printer, letters are drawn out of a dot matrix, and thus, varied fonts and arbitrary graphics can be produced. Because the printing involves mechanical pressure, these printers can create carbon copies and carbonless copies.

Each dot is produced by a tiny metal rod, also called a "wire" or "pin", which is driven forward by the power of a tiny electromagnet or solenoid, either directly or through small levers (pawls). Facing the ribbon and the paper is a small guide plate (often made of an artificial jewel such as sapphire or ruby) pierced with holes to serve as guides for the pins. The moving portion of the printer is called the print head, and when running the printer as a generic text device generally prints one line of text at a time. Most dot matrix printers have a single vertical line of dot-making equipment on their print heads; others have a few interleaved rows in order to improve dot density.



16- INKJET PRINTERS


Inkjet printers are a type of computer printer that operates by propelling tiny droplets of liquid ink onto paper.


17- DYE-SUBLIMATION PRINTER



A dye-sublimation printer (or dye-sub printer) is a computer printer which employs a printing process that uses heat to transfer dye to a medium such as a plastic card, printer paper or poster paper. The process is usually to lay one color at a time using a ribbon that has color panels. Most dye-sublimation printers use CMYO colors which differs from the more recognised CMYK colors in that the black dye is eliminated in favour of a clear overcoating. This overcoating (which has numerous names depending on the manufacturer) is effectively a thin laminate which protects the print from discoloration from UV light and the air while also rendering the print water-resistant. Many consumer and professional dye-sublimation printers are designed and used for producing photographic prints.


18- DIGITAL PRESS ( 1993)


Digital printing is the reproduction of digital images on a physical surface, such as common or photographic paper or paperboard-cover stock, film, cloth, plastic, vinyl, magnets, labels etc.

It can be differentiated from litho, flexography, gravure or letterpress printing in many ways, some of which are;

Every impression made onto the paper can be different, as opposed to making several hundred or thousand impressions of the same image from one set of printing plates, as in traditional methods.


The Ink or Toner does not absorb into the substrate, as does conventional ink, but forms a layer on the surface and may be fused to the substrate by using an inline fuser fluid with heat process(toner) or UV curing process(ink).


It generally requires less waste in terms of chemicals used and paper wasted in set up or makeready(bringing the image "up to color" and checking position).


It is excellent for rapid prototyping, or small print runs which means that it is more accessible to a wider range of designers and more cost effective in short runs.



19- 3D PRINTING


Three-dimensional printing is a method of converting a virtual 3D model into a physical object. 3D printing is a category of rapid prototyping technology. 3D printers typically work by 'printing' successive layers on top of the previous to build up a three dimensional object. 3D printers are generally faster, more affordable and easier to use than other additive fabrication technologies.


20- TECHNOLOGICAL DEVELOPMENTS



20.1 Woodcut



Woodcut is a relief printing artistic technique in printmaking in which an image is carved into the surface of a block of wood, with the printing parts remaining level with the surface while the non-printing parts are removed, typically with gouges. The areas to show 'white' are cut away with a knife or chisel, leaving the characters or image to show in 'black' at the original surface level. The block is cut along the grain of the wood (unlike wood engraving where the block is cut in the end-grain). In Europe beechwood was most commonly used; in Japan, a special type of cherry wood was popular.

Woodcut first appeared in ancient China. From 6th century onward, woodcut icons became popular and especially flourished in Buddhist texts. Since the 10th century, woodcut pictures appeared in inbetweenings of Chinese literature, and some banknotes, such as Jiaozi (currency). Woodcut New Year picture are also very popular with the Chinese.

In China and Tibet printed images mostly remained tied as illustrations to accompanying text until the modern period. The earliest woodblock printed book, the Diamond Sutra contains a large image as frontispiece, and many Buddhist texts contain some images. Later some notable Chinese artists designed woodcuts for books, the individual print develop in China in the form of New Year picture as an art-form in the way it did in Europe and Japan.

In Europe, Woodcut is the oldest technique used for old master prints, developing about 1400, by using on paper existing techniques for printing on cloth. The explosion of sales of cheap woodcuts in the middle of the century led to a fall in standards, and many popular prints were very crude. The development of hatching followed on rather later than in engraving. Michael Wolgemut was significant in making German woodcut more sophisticated from about 1475, and Erhard Reuwich was the first to use cross-hatching (far harder to do than in engraving or etching). Both of these produced mainly book-illustrations, as did various Italian artists who were also raising standards there at the same period. At the end of the century Albrecht Dürer brought the Western woodcut to a level that has never been surpassed, and greatly increased the status of the single-leaf (ie an image sold separately) woodcut.



20.2- Engraving


Engraving is the practice of incising a design onto a hard, flat surface, by cutting grooves into it. The result may be a decorated object in itself, as when silver, gold or steel are engraved, or may provide an intaglio printing plate, of copper or another metal, for printing images on paper, which are called engravings. Engraving was a historically important method of producing images on paper, both in artistic printmaking, and also for commercial reproductions and illustrations for books and magazines. It has long been replaced by photography in its commercial applications and, partly because of the difficulty of learning the technique, is much less common in printmaking, where it has been largely replaced by etching and other techniques. Other terms often used for engravings are copper-plate engraving and Line engraving. These should all mean exactly the same, but especially in the past were often used very loosely to cover several printmaking techniques, so that many so-called engravings were in fact produced by totally different techniques, such as etching.

In antiquity, the only engraving that could be carried out is evident in the shallow grooves found in some jewellery after the beginning of the 1st Millennium B.C. The majority of so-called engraved designs on ancient gold rings or other items were produced by chasing or sometimes a combination of lost-wax casting and chasing.

In the European Middle Ages goldsmiths used engraving to decorate and inscribe metalwork. It is thought that they began to print impressions of their designs to record them. From this grew the engraving of copper printing plates to produce artistic images on paper, known as old master prints in Germany in the 1430s. Italy soon followed. Many early engravers came from a goldsmithing background. The first and greatest period of the engraving was from about 1470 to 1530, with such masters as Martin Schongauer , Albrecht Dürer , and Lucas van Leiden.


20.3- Etching


Etching is the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio in the metal (the original process—in modern manufacturing other chemicals may be used on other types of material). As an intaglio method of printmaking it is, along with engraving, the most important technique for old master prints, and remains widely used today.


20.4- Halftoning


Halftone is the reprographic technique that simulates continuous tone imagery through the use of equally spaced dots of varying size. 'Halftone' can also be used to refer specifically to the image that is produced by this process.

The idea of halftone printing originates from William Fox Talbot. In the early 1850s he suggested using "photographic screens or veils" in connection with a photographic intaglio process.

Several different kinds of screens were proposed during the following decades, but the first half-tone photo-engraving process was invented by Canadians George-Édouard Desbarats and William Leggo Jr. On October 30, 1869, Desbarats published the Canadian Illustrated News which became the world’s first periodical to successfully employ this photo-mechanical technique; featuring a full page half-tone image of His Royal Highness Prince Arthur, from a photograph by Notman. Ambitious to exploit a much larger circulation, Debarats and Leggo went to New York and launched the New York Daily Graphic in March 1873, which became the world’s first illustrated daily.

The first truly successful commercial method was patented by Frederic Ives of Philadelphia in 1881. But although he found a way of breaking up the image into dots of varying sizes he did not make use of a ===screen===. In 1882 the German George Meisenbach patented a halftone process in England. His invention was based on the previous ideas of Berchtold and Swan. He used single lined screens which were turned during exposure to produce cross-lined effects. He was the first to achieve any commercial success with relief halftones.


20.5- Xerography


Xerography (or electrophotography) is a photocopying technique developed by Chester Carlson in 1938 and patented on October 6, 1942.

In 1937 Bulgarian physicist Georgi Nadjakov found that when placed into electric field and exposed to light, some dielectrics acquire permanent electric polarization in the exposed areas. That polarization persists in the dark and is destroyed in light. Chester Carlson, the inventor of photocopying, was originally a patent attorney and part-time researcher and inventor. His job at the patent office in New York required him to make a large number of copies of important papers. Carlson, who was arthritic, found this a painful and tedious process. This prompted him to conduct experiments with photoconductivity. Carlson experimented with "electrophotography" in his kitchen and in 1938, applied for a patent for the process. He made the first "photocopy" using a zinc plate covered with sulfur. The words "10-22-38 Astoria" were written on a microscope slide, which was placed on top of more sulfur and under a bright light. After the slide was removed, a mirror image of the words remained. Carlson tried to sell his invention to some companies, but because the process was still underdeveloped he failed. At the time multiple copies were made using carbon paper or duplicating machines and people did not feel the need for an electronic machine. Between 1939 and 1944, Carlson was turned down by over 20 companies, including IBM and GE, neither of which believed there was a significant market for copiers.

17) HEWLETT-PACKARD ( HP ) PRINTERS

by engr. AFAN BAHADUR KHAN




The Hewlett-Packard Company, commonly referred to as HP, is a technology corporation headquartered in Palo Alto, California, United States. HP is the largest technology company in the world and operates in nearly every country. HP specializes in developing and manufacturing computing, storage, and networking hardware, software and services. Major product lines include personal computing devices, enterprise servers, related storage devices, as well as a diverse range of printers and other imaging products. Other product lines, including electronic test equipment and systems, medical electronic equipment, solid state components and instrumentation for chemical analysis were spun off as Agilent Technologies in 1999.

HP markets its products to households, small to medium size businesses and enterprises both directly, via online distribution, consumer-electronics and office-supply retailers, software partners and major technology vendors.

HP posted US $91.7 billion in annual revenue in 2006 compared to US$91.4 billion for IBM, making it the world's largest technology vendor in terms of sales. In 2007 the revenue was $104 billion, making HP the first IT company in history to report revenues exceeding $100 billion.

HP is the largest worldwide seller of personal computers, surpassing rival Dell, according to market research firms Gartner and IDC reported in January 2008; the gap between HP and Dell widened substantially at the end of 2007, with HP taking a near 3.9% market share lead. HP is also the 5th largest software company in the world. It is one of the only American PC-focused computer companies publicly traded under the New York Stock Exchange.



1- COMPANY HISTORY


1.1- Founding



William (Bill) Hewlett and David (Dave) Packard both graduated in electrical engineering from Stanford University in 1935. The company originated in a garage in nearby Palo Alto during a fellowship they had with a past professor, Frederick Terman at Stanford during the Great Depression. Terman was considered a mentor to them in forming Hewlett-Packard.



The partnership was formalized in 1939 with an investment of US$538. Hewlett and Packard tossed a coin to decide whether the company they founded would be called Hewlett-Packard or Packard-Hewlett. Packard won the coin toss but named their electronics manufacturing enterprise the "Hewlett-Packard Company". HP incorporated on August 18, 1947, and went public on November 6, 1957.

Of the many projects they worked on, their very first financially successful product was a precision audio oscillator, the Model HP200A. Their innovation was the use of a small light bulb as a temperature dependent resistor in a critical portion of the circuit. This allowed them to sell the Model 200A for $54.40 when competitors were selling less stable oscillators for over $200. The Model 200 series of generators continued until at least 1972 as the 200AB, still tube-based but improved in design through the years. At 33 years, it was perhaps the longest-selling basic electronic design of all time.

One of the company's earliest customers was The Walt Disney Company, which bought eight Model 200B oscillators (at $71.50 each) for use in certifying the Fantasound surround sound systems installed in theaters for the movie Fantasia.



1.2- Early years



The company was originally rather unfocused, working on a wide range of electronic products for industry and even agriculture. Eventually they elected to focus on high-quality electronic test and measurement equipment.

From the 1940s until well into the 1990s the company concentrated on making electronic test equipment – signal generators, voltmeters, oscilloscopes, frequency counters, thermometers, time standards, wave analyzers, and many other instruments. A distinguishing feature was pushing the limits of measurement range and accuracy; many HP instruments were more sensitive, accurate, and precise than other comparable equipment.

Following the pattern set by the company's first product, the 200A, test instruments were labelled with three to five digits followed by the letter "A". Improved versions went to suffixes "B" through "E". As the product range grew wider HP started using product designators starting with a letter for accessories, supplies, software, and components.



1.3- The 1960s



HP is recognized as the symbolic founder of Silicon Valley, although it did not actively investigate semiconductor devices until a few years after the "Traitorous Eight" had abandoned William Shockley to create Fairchild Semiconductor in 1957. Hewlett-Packard's HP Associates division, established around 1960, developed semiconductor devices primarily for internal use. Instruments and calculators were some of the products using these devices.

HP partnered in the 1960s with Sony and the Yokogawa Electric companies in Japan to develop several high-quality products. The products were not a huge success, as there were high costs in building HP-looking products in Japan. HP and Yokogawa formed a joint venture (Yokogawa-Hewlett-Packard) in 1963 to market HP products in Japan. HP bought Yokogawa Electric's share of Hewlett-Packard Japan in 1999.

HP spun off a small company, Dynec, to specialize in digital equipment. The name was picked so that the HP logo "hp" could be turned upside down to be the logo "dy" of the new company. Eventually Dynec changed to Dymec, then was folded back into HP. HP experimented with using Digital Equipment Corporation minicomputers with its instruments. But after deciding that it would be easier to buy another small design team than deal with DEC, HP entered the computer market in 1966 with the HP 2100 / HP 1000 series of minicomputers. These had a simple accumulator-based design, with registers arranged somewhat similarly to the Intel x86 architecture still used today. The series was produced for 20 years, in spite of several attempts to replace it, and was a forerunner of the HP 9800 and HP 250 series of desktop and business computers.


1.4- The 1970s



The HP 3000 was an advanced stack-based design for a business computing server, later redesigned with RISC technology, that has only recently been retired from the market. The HP 2640 series of smart and intelligent terminals introduced forms-based interfaces to ASCII terminals, and also introduced screen labeled function keys, now commonly used on gas pumps and bank ATMs. Although scoffed at in the formative days of computing, HP would eventually surpass even IBM as the world's largest technology vendor in sales.

HP is identified by Wired magazine as the producer of the world's first marketed, mass-produced personal computer, the Hewlett-Packard 9100A, introduced in 1968. HP called it a desktop calculator because, as Bill Hewlett said, "If we had called it a computer, it would have been rejected by our customers' computer gurus because it didn't look like an IBM. We therefore decided to call it a calculator, and all such nonsense disappeared." An engineering triumph at the time, the logic circuit was produced without any integrated circuits; the assembly of the CPU having been entirely executed in discrete components. With CRT display, magnetic-card storage, and printer, the price was around $5000. The machine's keyboard was a cross between that of a scientific calculator and an adding machine. There was no alphabetical keyboard.

Steve Wozniak, co-founder of Apple, originally designed the Apple I computer while working at HP and offered it to them under their right of first refusal to his work, but they did not take it up as the company wanted to stay in scientific, business, and industrial markets.

The company earned global respect for a variety of products. They introduced the world's first handheld scientific electronic calculator in 1972 (the HP-35), the first handheld programmable in 1974 (the HP-65), the first alphanumeric, programmable, expandable in 1979 (the HP-41C), and the first symbolic and graphing calculator, the HP-28C. Like their scientific and business calculators, their oscilloscopes, logic analyzers, and other measurement instruments have a reputation for sturdiness and usability (the latter products are now part of spin-off Agilent's product line). The company's design philosophy in this period was summarized as "design for the guy at the next bench".

The 98x5 series of technical desktop computers started in 1975 with the 9815, and the cheaper 80 series, again of technical computers, started in 1979 with the 85. These machines used a version of the BASIC programming language which was available immediately after they were switched on, and used a proprietary magnetic tape for storage. HP computers were similar in capabilities to the much later IBM Personal Computer, although the limitations of available technology forced prices to be high.



1.5- The 1980s



In 1984, HP introduced both inkjet and laser printers for the desktop. Along with its scanner product line, these have later been developed into successful multifunction products, the most significant being single-unit printer/scanner/copier/fax machines. The print mechanisms in HP's tremendously popular LaserJet line of laser printers depend almost entirely on Canon's components (print engines), which in turn use technology developed by Xerox. HP develops the hardware, firmware, and software that convert data into dots for the mechanism to print.

In 1987, the Palo Alto garage where Hewlett and Packard started their business was designated as a California State historical landmark.



1.6- The 1990s


In the 1990s, HP expanded their computer product line, which initially had been targeted at university, research, and business customers, to reach consumers.

HP also grew through acquisitions, buying Apollo Computer in 1989 and Convex Computer in 1995.

Later in the decade HP opened hpshopping.com as an independent subsidiary to sell online, direct to consumers; in 2005 the store was renamed "HP Home & Home Office Store."

In 1999, all of the businesses not related to computers, storage, and imaging were spun off from HP to form Agilent. Agilent's spin-off was the largest initial public offering in the history of Silicon Valley. The spin-off created an $8 billion company with about 30,000 employees, manufacturing scientific instruments, semiconductors, optical networking devices, and electronic test equipment for telecom and wireless R&D and production.

In July 1999, HP appointed Carly Fiorina as CEO, the first female CEO of a company in the Dow Jones Industrial Average. Fiorina served as CEO during the tech downtown of the turn of the 2nd millenium. During her tenure, the market halved HP’s value commensurate with other tech companies at the time and the company incurred heavy job losses. The HP Board of Directors asked Fiorina to step down in 2005, and she resigned on February 9, 2005.



1.7- 2000 and beyond


Compaq merger. HP merged with Compaq in 2002. Compaq itself had bought Tandem Computers in 1997 (which had been started by ex-HP employees), and Digital Equipment Corporation in 1998. Following this strategy HP became a major player in desktops, laptops, and servers for many different markets. After the merger with Compaq, the new ticker symbol became "HPQ", a combination of the two previous symbols, "HWP" and "CPQ", to show the significance of the alliance. In 2006 hp outsourced its enterprise support to countries with lower cost workers: the Spanish support (for Spain) moved to Slovakia, the German support moved to Bulgaria, English support moved to Costa Rica, and so on.

EDS purchase. On May 13, 2008, HP and Electronic Data Systems announced [13] that they had signed a definitive agreement under which HP would purchase EDS. On June 30, HP announced that the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 had expired. "The transaction still requires EDS stockholder approval and regulatory clearance from the European Commission and other non-U.S. jurisdictions and is subject to the satisfaction or waiver of the other closing conditions specified in the merger agreement." The agreement was finalized on August 26, 2008 and it was publicly announced that EDS would be re-branded "EDS an HP company."

HP also expanded its presence in Israel first with the acqusistion in 2002 of Indigo Digital Press and in November 2005 with the acquisition of Scitex Vision from Scitex Corporation Ltd..

In October 2008, Hewlett-Packard (Canada) Co. was named one of "Canada's Top 100 Employers" by Mediacorp Canada Inc., and was featured in Maclean's newsmagazine. Later that month, Hewlett-Packard (Canada) Co. was also named one of Greater Toronto's Top Employers, which was announced by the Toronto Star newspaper.



2- TECHNOLOGY & PRODUCTS




HP has successful lines of printers, scanners, digital cameras, calculators, PDAs, servers, workstation computers, and computers for home and small business use computers; many of the computers came from the 2002 merger with Compaq. HP today promotes itself as supplying not just hardware and software, but also a full range of services to design, implement and support IT infrastructure.



The three business segments: Enterprise Storage and Servers (ESS), HP Services (HPS), and HP Software are structured beneath the broader Technology Solutions Group (TSG).


2.1- Imaging and Printing Group (IPG)




According to HP's 2005 U.S. SEC 10-K filing, HP's Imaging and Printing Group is "the leading imaging and printing systems provider in the world for printer hardware, printing supplies and scanning devices, providing solutions across customer segments from individual consumers to small and medium businesses to large enterprises." This division is currently headed by Vyomesh Joshi.



Products and technology associated with the Imaging and Printing Group include:

Inkjet and LaserJet printers, consumables and related products

Officejet all-in-one multifunction printer/scanner/faxes

Large Format Printers

Indigo Digital Press

HP Web Jetadmin printer management software

HP Output Management suite of software, including HP Output Server

LightScribe optical recording technology that laser-etches labels on disks

HP Photosmart digital cameras and photo printers

HP SPaM Hosted within IPG, SPaM is an internal consulting group that supports all HP businesses on mission-critical strategic and operation decisions.

On December 23, 2008, HP releases iPrint Photo for iPhone a free downloadable

software application that allows to print 4" x 6" photo.



2.2- Personal Systems Group (PSG)



HP's Personal Systems Group claims to be "one of the leading vendors of personal computers ("PCs") in the world based on unit volume shipped and annual revenue."[16]

Personal Systems Group products/technology include:

Business PCs and accessories

Consumer PCs and accessories including the HP Pavilion, Compaq Presario and VoodooPC series

Workstations for Unix, Windows and Linux systems

Handheld Computing including iPAQ Pocket PC handheld computing devices (from Compaq)

Digital "Connected" Entertainment including HP MediaSmart TVs, HP MediaSmart
Servers, HP MediaVaults, and DVD+RW drives. HP resold the Apple iPod until November 2005.

Home Storage Servers


2.3- Technology Solutions Group (TSG)




TSG incorporates Technical services, EDS, HP Software, Enterprise Storage and Servers Group (ESS) and ProCurve Networking.



2.4- Office of Strategy and Technology



HP's Office of Strategy and Technology, under Executive Vice President Shane Robison:

Steers the company's $3.6 billion research and development investment — including HP Labs.

Fosters the development of the company's global technical community.

Leads the company's strategy and corporate development efforts — including mergers, acquisitions, divestitures, intellectual property licensing, venture capital partnerships, and the ProCurve Networking Business Unit.

Performs worldwide corporate marketing activities — including external and internal communications, brand marketing, customer intelligence, and corporate affairs.


3- ENVIRONMENTAL RECORD



In 1998, the United States Environmental Protection Agency‎ sought a $2.5 million penalty against Hewlett Packard for violations against the Substance Control Act. The PA EPA alleged that the company had not filed a Pre-Manufacturing Notice (PMN) before it began manufacturing and exporting chemicals. Without filing these PMNs, the EPA cannot conduct risk analysis of new chemicals.

In 2002, Scorecard.org ranked Hewlett Packard facilities in the top 10-20 percentile for total environmental releases and top 30-40 percentile for air releases of recognized developmental toxicants. It also showed that HPs factory in Puerto Rico released 246 lb (112 kg) of air released TRI pollutants, and had a total of 483,136 lb (219,147 kg) of production related wastes.

In July 2007, the company announced that it had met its target, set in 2004, to recycle 1 billion pounds of electronics and toner and ink cartridges. It has set a new goal of recycling a further 2 billion pounds of hardware by the end of 2010. In 2006, the company recovered 187 million pounds of electronics, 73 percent more than its closest competitor.



4- HP CERTIFIED PROFESSIONALS



Hewlett-Packard's Certified Professional (HP-CP) program was developed to confirm the technical skills, sales competencies and knowledge that is required to propose and deploy, service and support technology and solutions sold by HP. HP-CP is intended for customers, resellers, and HP employees.


5- SPONSORSHIPS



HP has many sponsorships. One well known sponsorship is of Walt Disney World's Epcot Park's Mission: SPACE. Others can be found on Hewlett-Packard's website . From 1995 to 1999 they were the shirt sponsor of English Premier League club Tottenham Hotspur. They also sponsored the BMW Williams Formula 1 team. Hewlett-Packard also has the naming rights arrangement for the HP Pavilion at San Jose, home of the San Jose Sharks NHL hockey team.



6- PRODUCT LEGACY



Agilent Technologies, not HP, retains the direct product legacy of the original company founded in 1939. Agilent's current portfolio of electronic instruments are descended from HP's very earliest products. HP entered the computer business only after its instrumentation competencies were well-established.

After the acquisition of Compaq in 2002, HP has maintained the "Compaq Presario" brand on low-end home desktops and laptops, the "HP Compaq" brand on business desktops and laptops, and the "HP ProLiant" brand on Intel-architecture servers. (The "HP Pavilion" brand is used on home entertainment laptops and all home desktops.)

HP uses DEC's "StorageWorks" brand on storage systems; Tandem's "NonStop" servers are now branded as "HP Integrity NonStop".

16) LASER PRINTERS

by engr. AFAN BAHADUR KHAN




A laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper. As with digital photocopiers and multifunction printers (MFPs), laser printers employ a xerographic printing process but differ from analog photocopiers in that the image is produced by the direct scanning of a laser beam across the printer's photoreceptor.




1- OVERVIEW




A laser beam projects an image of the page to be printed onto an electrically charged rotating drum coated with selenium. Photoconductivity removes charge from the areas exposed to light. Dry ink (toner) particles are then electrostatically picked up by the drum's charged areas. The drum then prints the image onto paper by direct contact and heat, which fuses the ink to the paper.



Laser printers have many significant advantages over other types of printers. Unlike impact printers, laser printer speed can vary widely, and depends on many factors, including the graphic intensity of the job being processed. The fastest models can print over 200 monochrome pages per minute (12,000 pages per hour). The fastest color laser printers can print over 100 pages per minute (6000 pages per hour). Very high-speed laser printers are used for mass mailings of personalized documents, such as credit card or utility bills, and are competing with lithography in some commercial applications.

The cost of this technology depends on a combination of factors, including the cost of paper, toner, and infrequent drum replacement, as well as the replacement of other consumables such as the fuser assembly and transfer assembly. Often printers with soft plastic drums can have a very high cost of ownership that does not become apparent until the drum requires replacement.

A duplexing printer (one that prints on both sides of the paper) can halve paper costs and reduce filing volumes. Formerly only available on high-end printers, duplexers are now common on mid-range office printers, though not all printers can accommodate a duplexing unit. Duplexing can also give a slower page-printing speed, because of the longer paper path.

In comparison with the laser printer, most inkjet printers and dot-matrix printers simply take an incoming stream of data and directly imprint it in a slow lurching process that may include pauses as the printer waits for more data. A laser printer is unable to work this way because such a large amount of data needs to output to the printing device in a rapid, continuous process. The printer cannot stop the mechanism precisely enough to wait until more data arrives, without creating a visible gap or misalignment of the dots on the printed page.

Instead the image data is built up and stored in a large bank of memory capable of representing every dot on the page. The requirement to store all dots in memory before printing has traditionally limited laser printers to small fixed paper sizes such as letter or A4. Most laser printers are unable to print continuous banners spanning a sheet of paper two meters long, because there is not enough memory available in the printer to store such a large image before printing begins.



2- HISTORY



The laser printer was invented at Xerox in 1969 by researcher Gary Starkweather, who had an improved printer working by 1971 and incorporated into a fully functional networked printer system by about a year later. The prototype was built by modifying an existing xerographic copier. Starkweather disabled the imaging system and created a spinning drum with 8 mirrored sides, with a laser focused on the drum. Light from the laser would bounce off the spinning drum, sweeping across the page as it traveled through the copier. The hardware was completed in just a week or two, but the computer interface and software took almost 3 months to complete.

The first commercial implementation of a laser printer was the IBM model 3800 in 1976, used for high-volume printing of documents such as invoices and mailing labels. It is often cited as "taking up a whole room," implying that it was a primitive version of the later familiar device used with a personal computer. While large, it was designed for an entirely different purpose. Many 3800s are still in use.[citation needed]

The first laser printer designed for use with an individual computer was released with the Xerox Star 8010 in 1981. Although it was innovative, the Star was an expensive ($17,000) system that was purchased by only a relatively small number of businesses and institutions. After personal computers became more widespread, the first laser printer intended for a mass market was the HP LaserJet 8ppm, released in 1984, using a Canon engine controlled by HP software. The HP LaserJet printer was quickly followed by laser printers from Brother Industries, IBM, and others.

As with most electronic devices, the cost of laser printers has fallen markedly over the years. In 1984, the HP LaserJet sold for $3500[3], had trouble with even small, low resolution graphics, and weighed 71 pounds (32 kg). Low end monochrome laser printers often sell for less than $75 as of 2008. These printers tend to lack onboard processing and rely on the host computer to generate a raster image (see Winprinter), but still will outperform the LaserJet Classic in nearly all situations.



3- HOW IT WORKS


There are typically seven steps involved in the laser printing process:


3.1- Raster image processing




Each horizontal strip of dots across the page is known as a raster line or scan line. Creating the image to be printed is done by a Raster Image Processor (RIP), typically built into the laser printer. The source material may be encoded in any number of special page description languages such as Adobe PostScript (PS) , HP Printer Command Language (PCL), or Microsoft XML Page Specification (XPS) , as well as unformatted text-only data. The RIP uses the page description language to generate a bitmap of the final page in the raster memory. Once the entire page has been rendered in raster memory, the printer is ready to begin the process of sending the rasterized stream of dots to the paper in a continuous stream.


3.2- Charging



A corona wire (in older printers) or a primary charge roller projects an electrostatic charge onto the photoreceptor (otherwise named the photoconductor unit), a revolving photosensitive drum or belt, which is capable of holding an electrostatic charge on its surface while it is in the dark.



Numerous patents describe the photosensitive drum coating as a silicon sandwich with a photocharging layer, a charge leakage barrier layer, as well as a surface layer. One version uses amorphous silicon containing hydrogen as the light receiving layer, Boron nitride as a charge leakage barrier layer, as well as a surface layer of doped silicon, notably silicon with oxygen or nitrogen which at sufficient concentration resembles machining silicon nitride; the effect is that of a light chargeable diode with minimal leakage and a resistance to scuffing.


3.3- Exposing




The laser is aimed at a rotating polygonal mirror, which directs the laser beam through a system of lenses and mirrors onto the photoreceptor. The beam sweeps across the photoreceptor at an angle to make the sweep straight across the page; the cylinder continues to rotate during the sweep and the angle of sweep compensates for this motion. The stream of rasterized data held in memory turns the laser on and off to form the dots on the cylinder. (Some printers switch an array of light emitting diodes spanning the width of the page, but these devices are not "Laser Printers".) Lasers are used because they generate a narrow beam over great distances. The laser beam neutralizes (or reverses) the charge on the white parts of the image, leaving a static electric negative image on the photoreceptor surface to lift the toner particles.


3.4- Developing



The surface with the latent image is exposed to toner, fine particles of dry plastic powder mixed with carbon black or coloring agents. The charged toner particles are given a negative charge, and are electrostatically attracted to the photoreceptor where the laser wrote the latent image. Because like charges repel, the negatively charged toner will not touch the drum where light has not removed the negative charge.

The overall darkness of the printed image is controlled by the high voltage charge applied to the supply toner. Once the charged toner has jumped the gap to the surface of the drum, the negative charge on the toner itself repels the supply toner and prevents more toner from jumping to the drum. If the voltage is low, only a thin coat of toner is needed to stop more toner from transferring. If the voltage is high, then a thin coating on the drum is too weak to stop more toner from transferring to the drum. More supply toner will continue to jump to the drum until the charges on the drum are again high enough to repel the supply toner. At the darkest settings the supply toner voltage is high enough that it will also start coating the drum where the initial unwritten drum charge is still present, and will give the entire page a dark shadow.



3.5- Transferring



The photoreceptor is pressed or rolled over paper, transferring the image. Higher-end machines use a positively charged transfer roller on the back side of the paper to pull the toner from the photoreceptor to the paper.


3.6- Fusing




The paper passes through rollers in the fuser assembly where heat and pressure (up to 200 Celsius) bond the plastic powder to the paper.
One roller is usually a hollow tube (heat roller) and the other is a rubber backing roller (pressure roller). A radiant heat lamp is suspended in the center of the hollow tube, and its infrared energy uniformly heats the roller from the inside. For proper bonding of the toner, the fuser roller must be uniformly hot.

The fuser accounts for up to 90% of a printer's power usage. The heat from the fuser assembly can damage other parts of the printer, so it is often ventilated by fans to move the heat away from the interior. The primary power saving feature of most copiers and laser printers is to turn off the fuser and let it cool. Resuming normal operation requires waiting for the fuser to return to operating temperature before printing can begin.

Some printers use a very thin flexible metal fuser roller, so there is less mass to be heated and the fuser can more quickly reach operating temperature. This both speeds printing from an idle state and permits the fuser to turn off more frequently to conserve power.

If paper moves through the fuser more slowly, there is more roller contact time for the toner to melt, and the fuser can operate at a lower temperature. Smaller, inexpensive laser printers typically print slowly, due to this energy-saving design, compared to large high speed printers where paper moves more rapidly through a high-temperature fuser with a very short contact time.


3.7- Cleaning

When the print is complete, an electrically neutral soft plastic blade cleans any excess toner from the photoreceptor and deposits it into a waste reservoir, and a discharge lamp removes the remaining charge from the photoreceptor.

Toner may occasionally be left on the photoreceptor when unexpected events such as a paper jam occur. The toner is on the photoconductor ready to apply, but the operation failed before it could be applied. The toner must be wiped off and the process restarted.

Waste toner cannot be reused for printing because it can be contaminated with dust and paper fibers. A quality printed image requires pure, clean toner. Reusing contaminated toner can result in splotchy printed areas or poor fusing of the toner into the paper. There are some exceptions however, most notably some Brother and Toshiba laser printers, which use a patented method to clean and recycle the waste toner.


3.8- Multiple steps occurring at once



Once the raster image generation is complete all steps of the printing process can occur one after the other in rapid succession. This permits the use of a very small and compact unit, where the photoreceptor is charged, rotates a few degrees and is scanned, rotates a few more degrees and is developed, and so forth. The entire process can be completed before the drum completes one revolution.

Different printers implement these steps in distinct ways. Some "laser" printers actually use a linear array of light-emitting diodes to "write" the light on the drum (see LED printer). The toner is based on either wax or plastic, so that when the paper passes through the fuser assembly, the particles of toner melt. The paper may or may not be oppositely charged. The fuser can be an infrared oven, a heated pressure roller, or (on some very fast, expensive printers) a xenon flash lamp. The Warm Up process that a laser printer goes through when power is initially applied to the printer consists mainly of heating the fuser element. Many printers have a toner-conservation mode, called "Economode" by Hewlett-Packard, which uses about half as much toner but produces a lighter draft-quality output.



4- COLOR LASER PRINTERS


Color laser printers use colored toner (dry ink), typically cyan, magenta, yellow, and black (CMYK), with a printing pass for each toner color.



Color adds complexity to the printing process because very slight misalignments known as registration errors can occur between printing each color, causing unintended color fringing, blurring, or light/dark streaking along the edges of colored regions. To permit a high registration accuracy, some color laser printers use a large belt the size of a full sheet of paper to generate the image. All three or four layers of toner are precisely applied to the belt, and the combined layers are then applied to the paper in a single step.

Color laser printers typically require four times as much memory as a monochrome printer to print the same size document, because each of the three CMY or four CMYK color separations needs to be rasterized and stored in memory before printing can begin.



5- DPI RESOLUTIONS



1200 DPI printers are commonly available during 2008.

2400 DPI electrophotographic printing plate makers, essentially laser printers that print on plastic sheets, are also available.



6- LASER PRINTER MAINTENANCE


Most consumer and small business laser printers use a cartridge that combines the photoreceptor (sometimes called "photoconductor unit") with the supply toner and waste toner bottles and various wiper blades. When the supply toner is consumed, replacing the cartridge automatically replaces the photoreceptor, waste toner bottle, and blades.

Some small consumer printers use a separate toner bottle that can be replaced several times separately from the photoreceptor, allowing for a much lower cost of operation. High-volume business laser printers separate all components into individual modules.

After printing about fifty thousand pages, typical maintenance is to vacuum the mechanism, and clean or replace the paper handling rollers. The rollers have a thick rubber coating, which eventually suffers wear and becomes covered with slippery paper dust. They can usually be cleaned with a damp lint-free rag and there are chemical solutions that can help restore the traction of the rubber.

After one hundred thousand pages, it is common for the fuser assembly to either wear out or need replacing. The fuser heating rollers are often coated with an oil that prevents toner from sticking to the rollers. A small amount of the oil coating is absorbed by each piece of paper passing through the fuser, eventually requiring the oil supply to be replenished or the pressure roller assembly to be completely replaced. It is common for the fuser assembly to be left unmaintained until the toner starts sticking to the rollers, which creates a repeating ragged line on every printed page due to the rollers not being smooth anymore.

Color laser printers are typically more expensive and higher maintenance than monochrome laser printers since they contain more imaging components. Color laser printers intended for high volume use may require supplies that monochrome printers do not use, while the least expensive consumer color laser printers are expected to wear out and fail four times faster during color printing, compared to monochrome printing.

Due to current market incentives, the least expensive consumer color laser printers often cost less than the total value of the replacement parts inside the printer. The photoreceptor assembly for example may last 100,000 pages but may cost as much to replace as buying a new printer with new toner cartridges included.



7- SAFETY HAZARDS, HEALTH RISKS, & PRECAUTION



7.1- Shock hazards



Although modern printers include many safety interlocks and protection circuits, it is possible for a high voltage or a residual voltage to be present on the various rollers, wires, and metal contacts inside a laser printer. Care should be taken to avoid unnecessary contact with these parts to reduce the potential for painful electrical shock.


7.2- Toner clean-up



Toner particles are designed to have electrostatic properties and can develop static-electric charges when they rub against other particles, objects, or the interiors of transport systems and vacuum hoses. Because of this and its small particle size, toner should not be vacuumed with a conventional home vacuum cleaner. Static discharge from charged toner particles can ignite dust in the vacuum cleaner bag or create a small explosion if sufficient toner is airborne. This may damage the vacuum cleaner or start a fire. In addition, toner particles are so fine that they are poorly filtered by conventional household vacuum cleaner filter bags and blow through the motor or back into the room.

Toner particles melt (or fuse) when warmed. Small toner spills can be wiped up with a cold, damp cloth.

If toner spills into the laser printer, a special type of vacuum cleaner with an electrically conductive hose and a high efficiency (HEPA) filter may be needed for effective cleaning. These are called ESD-safe (Electrostatic Discharge-safe) or toner vacuums. Similar HEPA-filter equipped vacuums should be used for clean-up of larger toner spills.

Toner is easily cleaned from most water-washable clothing. As toner is a wax or plastic powder with a low melting temperature, it must be kept cold during the cleaning process. Washing a toner stained garment in cold water is often successful. Even warm water is likely to result in permanent staining. The washing machine should be filled with cold water before adding the garment. Washing through two cycles improves the chances of success. The first may use hand wash dish detergent, with the second cycle using regular laundry detergent. Residual toner floating in the rinse water of the first cycle will remain in the garment and may cause a permanent graying. A clothes dryer or iron should not be used until it is certain that all the toner has been removed.


7.3- Ozone hazards



As a natural part of the printing process, the high voltages inside the printer can produce a corona discharge that generates a small amount of ionized oxygen and nitrogen, forming ozone and nitrogen oxides. In larger commercial printers and copiers, a carbon filter in the air exhaust stream breaks down these oxides to prevent pollution of the office environment.

However, some ozone escapes the filtering process in commercial printers, and ozone filters are not used in many smaller consumer printers. When a laser printer or copier is operated for a long period of time in a small, poorly ventilated space, these gases can build up to levels at which the odor of ozone or irritation may be noticed. A potential for creating a health hazard is theoretically possible in extreme cases.


7.4- Respiratory health risks



According to a recent study conducted in Queensland, Australia, some printers emit sub-micrometre particles which some suspect may be associated with respiratory diseases. Of 63 printers evaluated in the Queensland University of Technology study, 17 of the strongest emitters were made by Hewlett-Packard and one by Toshiba. The machine population studied, however, was only those machines already in place in the building and was thus biased toward specific manufacturers. The authors noted that particle emissions varied substantially even among the same model of machine. According to Professor Morawska of Queensland University, one printer emitted as many particles as a burning cigarette.

"The health effects from inhaling ultrafine particles depend on particle composition, but the results can range from respiratory irritation to more severe illness such as cardiovascular problems or cancer." (Queensland University of Technology).
A 2006 study in Japan found that laser printers increase concentrations of styrene, xylenes, and ozone, and that ink-jet printers emitted pentanol.

Muhle et al. (1991) reported that the responses to chronically inhaled copying toner, a plastic dust pigmented with carbon black, titanium dioxide and silica were also similar qualitatively to titanium dioxide and diesel exhaust.