Teletype ASR 33
The Teletype Model 33 is an electro-mechanical teleprinter designed for light-duty office. Introduced in 1963, it was one of the most popular terminals in the data-communications industry. The MIL Mod 8 (and Mod 80) was designed to interface with this specific teletype, hence why I have a page dedicated to it.
The Model 33 ASR, (Automatic Send and Receive), has a built-in 8-level punched tape reader and tape punch; which allows the user to save and record programs.
The interface is a 20 mA current loop (the standard serial protocol for computer terminals before the rise of RS-232) that operates at 110 baud. The Model 33 used the seven-bit upper-case only ASCII code, also known as CCITT International Telegraphic Alphabet No. 5.
The Model 33 ASR, (Automatic Send and Receive), has a built-in 8-level punched tape reader and tape punch; which allows the user to save and record programs.
The interface is a 20 mA current loop (the standard serial protocol for computer terminals before the rise of RS-232) that operates at 110 baud. The Model 33 used the seven-bit upper-case only ASCII code, also known as CCITT International Telegraphic Alphabet No. 5.
Teletype ASR 33 Documentation
Bell System Practice Documents (Division 570)
The Bell System Practices (BSPs) are a compilation of technical publications which describes the best methods of engineering, constructing, installing, and maintaining the telephone plant of the Bell System under direction of AT&T and Bell Telephone Laboratories.
The format of BSP designations is a nine-digit numerical format, written in three groups of three digits. The first three digits referred to the division, which indicated a broad subject area. The next three digits indicated a specific subject area, such as specific type of equipment used within the major division subject. The final three digits indicate the serial number of the document. The content could be general descriptive information, information on wiring and connections, test procedures, or piece-part replacement and repair information. Division 570 deals with teletypes.
The format of BSP designations is a nine-digit numerical format, written in three groups of three digits. The first three digits referred to the division, which indicated a broad subject area. The next three digits indicated a specific subject area, such as specific type of equipment used within the major division subject. The final three digits indicate the serial number of the document. The content could be general descriptive information, information on wiring and connections, test procedures, or piece-part replacement and repair information. Division 570 deals with teletypes.
General Documentation (574-100)
Teletype Corporation's manuals use the numbering scheme used for Bell System Practices. Teletype's manuals for the Model 33 are all in Division 574.
Keyboard (574-121)
Typing Unit (574-122)
Call Control Unit (574-123)
Tape Reader (574-124)
Tape Punch (574-125)
Cover (574-126)
Videos covering ASR33 Restoration by CuriousMarc
Youtuber CuriousMarc produced a series of excellent videos on restoration of an ASR 33 that nearly needed every component adjusted or repaired. This is an excellent resource if you have a Teletype ASR 33 and need some idea where to begin troubleshooting. He has also produced a good set of videos on a Model 19 Teletype restoration as well, so be sure to check out his channel.
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Last updated on October 24, 2023 (Links fixed)