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Dead medium: IBM Letterwriter
From: (Bradley O'Neill)
Source(s): Information and Secrecy: Vannevar Bush, Ultra, and the Other Memex, by Colin Burke, Scarecrow Press, Metuchen N.J. 1994. LC# HD9696.C772B87 1994.

pages 248-249

IBM LETTERWRITER: 1941-1942. Analytical/data processing machines cobbled together as a stopgap immediately following Pearl Harbor, built for the US Naval cryptanalytic branch, OP-20-G.

"[Letterwriters] linked teletype, tape, card, and film media together. From unpretentious beginnings as data input equipment, the IBM Letterwriters blossomed into a number of increasingly complex machines that were used for a wide range of analytical tasks. The Letterwriter system tied special electric typewriters to automatic tape and card punches and eventually to film processing machines. Such automation of data processing was badly needed at OP- 20-G. Without automation, [OP-20-G] would have been unable to receive and process its wartime load of a million words a day."

pages 249-250

"The system centered about a special electric typewriter, a tape punch, and a tape reader. The typewriter was a modified version of IBM's expensive Electromatic machine. The tape punch and tape reader were bread-box sized metal frames filled with relays and sensing pins. The relays controlled reading and punching and were used to convert the teletype code to the signals needed by OP-20-G's other machines. Linked together, the punch, the reader, and typewriter covered the top of a large desk. It was hoped they would eventually allow the creation of machine-ready data directly from OP-20-G's new international telegraph system."

"Simple changes made the Letterwriter equipment useful for another very important but time consuming task, the analysis of (((encryption device))) wheel settings. When an analyst thought he had found the correct combinations on an enemy system he would set a copy of the encryption machine's wheels, lugs, and plugboards and type in parts of the encrypted message. He then examined the output to see if it was sensible."

"Despite their usefulness and reliability, there was a drawback to the Letterwriters. They were not rapid machines. Because of the limits set by the mechanical nature of typewriters and the punches, the system ran at eight characters per second or only 480 characters per minute."