The ASR-33 Teletype

The Teletype machine was not designed to communicate with computers, it was designed to communicate with other Teletype machines. Basically, it was a wired-up typewriter. Type a letter on a California Teletype and it prints out on a New York Teletype. Like the fax machines that eventually replaced it, the Teletype was invaluable to banks, businesses, law enforcement, and the press. Heavy-duty Model 15 Teletypes chugging away day and night in wire service offices across the country created the background music of the breaking story.

So where do computers come in? As late as 1970 a Teletype Corporation brochure barely mentioned computers. But for computer users in the 1960s, particularly those setting up timesharing systems, the Teletype was a natural input and output device. By then Teletypes generally transmitted serial streams of ASCII-encoded binary data, which was also used by the best timesharing computers of the day. And the punched paper tape that Teletype machines produced for retransmission of messages provided a convenient means of storing and inputting computer programs.

The high-end Model 35 Teletype was ideal if you could afford it, but the model that became the ubiquitous symbol of timesharing was the the Model ASR-33. This was an inexpensive machine for light duty work, two or three hours a day. Under the heavy fingers of relentless computer students, parts bent and broke with frustrating regularity.

The Teletype machine defined the computer interface for nearly two decades. It was replaced in the late ’70s by inexpensive keyboards and monitors, but until the Apple Macintosh came along in 1984 those monitors were generally used as “glass teletypes,” presenting the user with an electronic version of the Teletype’s command-line interface.