Line Printer - Introduction

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Friends in our last posts we have discussed about the introduction of Printers and the Dot Matrix Printer. Today we shall discuss about Line Printers. Line printers are impact printers. A line printer produces line of characters all at once. It is a fast device and the speed varies from 100 to over 3000 LPM (Lines Per Minute).

There are two types of line printers. Those are

1. Drum Printers and
2. Chain Printers

A Drum Printer uses a solid, cylindrical drum which rotates at a rapid speed. A complete character set is raised into bosses (or bands) around the circumference of a drum at all the possible print positions. Thus a printer that can print upto 132 characters per line, there are 132 characters set tolled on its surface. A set of print hammers for each possible print position are located infront of a drum. These hammers are activated to strike the paper and an inked ribbon against the approximate character on the drum as the correct character is rotated into position. Thus the entire line can be printed in one revolution of drum. Speeds of over 3000 lines per minute are possible with drum printers. The limitation of drum printers is printer drums are expensive and have a fixed font. Have a look at the cylinder of a drum printer below.

Cylinder of a Drum Printer

A chain Printer consists of rapidly rotating chain called print chain, having more than one complete character sets, which revolves continuously in-front of the print line. As the chain rotates, print hammers activate to strike the paper and a ribbon against the selected character on chain. Since the entire character set is repeated around the chain, it is not necessary to wait for the chain to make a complete revolution to position the desired character in the correct print position. The speed of these printers varies from 400 to 2400 LPM. Some chain printers are metal band instead of a chain.

Chain Printer

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