Teletype Model 28

The Teletype Model 28 is a product line of page printers, typing and non-typing tape perforator and tape reperforators, fixed head single contact and pivoted head multi-contact transmitter-distributors, and receiving selector equipment. Regarded as the most rugged machines Teletype Corporation built, this line of teleprinters used an exchangeable type box for printing and sequential selector "Stunt Box" to mechanically initiate non-printing functions within the typing unit of the page printer, electrically control functions within the page printer and electrically control external equipment.

The Teletype Model 28 is more rugged and more expensive than later Teletype Model 32 machines. The Teletype Corporation introduced the Model 28 as a commercial product in 1953 after being originally designed for the United States military.

There are three versions of the Model 28 page printer:

Teletype Corporation's Model 28 line of communications terminals was first delivered to the US Military in 1951 and commercially introduced in 1953. This series of teleprinters and associated equipment was popular in the various branches of the United States Armed Forces, and commercially in the financial and manufacturing industries.

Teletype machines were gradually replaced in new installations by dot-matrix printers and CRT-based terminals in the mid to late 1970s. Basic CRT-based terminals which could only print lines and scroll them are often called glass teletypes to distinguish them from more sophisticated devices.

Teletype Corporation discontinued Model 28 production in 1981.

While the manufacturer called the Model 28 teleprinter with a tape punch and tape reader a Model 28 ASR, many users, specifically computer users, called this equipment an ASR-28. The earliest known source for this Teletype Corporation equipment naming discrepancy comes from Digital Equipment Corporation documentation where the September 1963 PDP-4 Brochure calls the Teletype Model 28 KSR a "KSR-28" in the paragraph titled "Printer-Keyboard and Control Type 65". This naming discrepancy continued from the Teletype Model 28 to other Teletype equipment in later DEC documentation.

The design objective for the Model 28 was a machine that would run at 100 words-per-minute with less maintenance than that required by a contemporary teletypewriter running at 60 words-per-minute. Additional design criteria included the requirements to run quieter and be lighter than previous teleprinters. The Model 28 equipment was also designed to successfully operate in a wider range of temperatures and operate in moving vehicles. The Model 28 equipment adjustments are made by turning screws and not by bending metal bars and levers as is done in the later Model 32 and Model 33 series of teleprinters. The Model 28 printing unit frame is lighter due to the use of stamped sheet metal instead of cast iron. The Model 28 ASR allowed the user to operate the keyboard to punch tape while transmitting a previously punched tape and to punch a tape while printing an incoming message.

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