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Dot Matrix Printers

Posted by Big Boo on June 27th, 2011

Dot Matrix PrinterToday, most households with a home PC probably also have a printer that is capable of printing full colour near photo quality pictures, and we kind of take it for granted. Most will own an ink jet style printer that cost less than 100 pounds (probably less than 50 pounds) and we tend to take it for granted really.

As recently as the 1980s though this would have almost have been deemed witchcraft! Back then printers cost as much, if not more, than the computer they were connected to, and you were often limited to a mere handful of printers that your home computer could actually connect to (it was no doubt made by the company that made your computer too).

If you did have access to a printer back then, be it at home, work or school, chances are it was a dot matrix printer. These printers worked in a similar manner to a typewriter. Mounted on a rail inside the printer was the print head, which was a little device that had a row of pins that could each be pushed out individually.

The pins were fired out at speed towards an inked ribbon which was just in front of the paper. The pins pushed the ribbon against the paper and thus left a dot on the paper. The pins retracted, the print head then moved a small distance along the rail, and a different selection of pins would fire out. By varying which pins were pushed forward, characters could be printed on the paper.

Whilst this is pretty clever, there were several drawbacks. Firstly, being a mechanical operation limited the speed at which the printer could operate, so dot matrix printers were often slow.

Secondly, the act of firing out the pins made them quite noisy.

Thirdly, you were limited by how many pins the print head could have, which affected the quality of the final print out. Probably the most common arrangements were to have 9 or 24 pins on the print head.

Fourthly, at least initially most dot matrix printers couldn’t handle printing on individual sheets of paper, so instead you had to have a great big box of continuous paper that had little holes running down each side. The little holes were used to pull the paper through the printer, as they were attached to a couple of little sprocket wheels. Sometimes this paper had little green lines printed across it so that it was easier to see the individual lines of printed text.

Most dot matrix printers were also only capable of printing in black and white, but they could at least print graphics as well as text since the printer driver just had to fire out the correct arrangement of pins.

Colour dot matrix printers were also available though, and these worked by having a ribbon with the four printing colours on (cyan, magenta, yellow and black). The ribbon could be moved up and down so that the pins of the print head were all behind a particular colour, and by printing the line four times using the different parts of the ribbon a colour image could be created, although it was by no means photographic quality.

Ink jet printers may make this system look archaic now, but the good old dot matrix printer isn’t quite ready to keel over and die just yet. They still have an admittedly diminishing role in the modern world, as any business that uses multi-part carbonated stationery on a regular basis will tell you.