The NCR-340 was
NCR's first line "High Speed" 300-line-per-minute
computer printer
In computing, a printer is a peripheral machine which makes a persistent representation of graphics or text, usually on paper. While most output is human-readable, bar code printers are an example of an expanded use for printers. Differ ...
. It used a drum made up of 120 (later 132) hardened steel discs with the upper-case alphabet, the numbers 0-9 and a few special symbols.
The discs were keyed on an armature, but could be changed if a character were damaged.
The drum sat above an ink
ribbon
A ribbon or riband is a thin band of material, typically cloth but also plastic or sometimes metal, used primarily as decorative binding and tying. Cloth ribbons are made of natural materials such as silk, cotton, and jute and of synthetic mater ...
. Below the ribbon the
green-bar continuous form paper was moved into and out of the printer head on four tractor assemblies. Below the paper path were a set of 120 or 132 “hammers” that were triggered by electric
solenoid
upright=1.20, An illustration of a solenoid
upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines
A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whose ...
s.
Each line of a report was sent from the 315 to the printer and loaded into a buffer. As the print drum spun, a glass timing disc on one end would indicate to the internal logic that a character was in position to be printed. All of the “A” characters in the buffer would trigger the appropriate hammer to fire. The hammer would force the paper up against the ribbon, and hit the “A” character on the spinning drum for its position in the line. This would continue for one revolution of the drum printing.
The printer could print up to eight copies of a report by using carbon paper between each layer of paper. There was a whole industry and series of auxiliary machine (
collators) that would separate the different copies of the report and remove the carbons. Then the continuous reports were sent through a burster to separate individual pages.
References
{{NCR Corp
Impact printers
NCR Corporation products