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Subject: Dead Media Working Note 03.3
Dead Medium: IBM Letterwriter
From: boneill_AT_allinux1.alliance.net (Bradley O'Neill)
Source: 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."
Dead
Media | 0.01-02.0 | 02.1-04.0
| 04.1-06.0 | 06.1-08.0 |
08.1-10.0 | 10.1-12.0 |