Teletype Model 28
The Teletype Model 28 is a product line of teleprinters, typing and non-typing tape perforator and tape reperforators, fixed head single contact and pivoted head multi-contact transmitter-distributors, and receiving selector equipment.
The Teletype Corporation introduced the Model 28 as a commercial product in 1953 after being originally designed for the United States military.
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.
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".
Additional design criteria included the requirements to run quieter and be lighter than previous teleprinters.
The Model 28 printing unit frame is lighter due to the use of stamped sheet metal instead of cast iron.
Another design advance in the Model 28 was the use of a new all-steel clutch that uses internal expansion to minimize wear and reduce the need for lubrication.
A separate shelf is available in the console base for ancillary equipment such as rectifiers and is also used to store local installation documentation.
The recommended operating environment is a temperature of 40 to 110 Fahrenheit, a relative humidity of 2 to 95 percent and an altitude of 0 to 10,000 feet.
The Model 28 ASR keyboard base (LAK) supports the tape punch in addition to motor unit (LMU), typing unit (LP) and the code selecting and signal generator mechanisms of the Model 28 KSR.
The recommended operating environment is a temperature of 40 to 110 Fahrenheit, a relative humidity of 2 to 95 percent and an altitude of 0 to 10,000 feet.
Model 28 Receive Only Page Printer The Teletype Model 28 RO is composed of a receive-only base (LB) which supports the motor unit and the typing unit (LP) and incorporates the code selecting mechanisms.
In some equipment, these electrical signals are transmitted over a single asynchronous serial telegraph channel to local or remote receiving stations.
The receiving unit accepts incoming electrical signals and punches and prints the intelligence on five-level paper tape.
The sending unit reads and translates the taped intelligence into electrical impulses for transmission either cross-office or cross-country.
There were different kinds of Model 28 interfaces that included Rotary Dial, current loop and polar signaling.
The Model 35 line, built for ASCII, used a similar mechanical structure and shared numerous parts.
