ASR-33

ASR-33. The ASR-33 was a landmark teleprinter manufactured by the Teletype Corporation, introduced in 1963. It became a ubiquitous input/output device for early minicomputer systems and time-sharing networks due to its reliability and relatively low cost. Combining a keyboard, printer, and paper tape reader/punch, it served as a primary interface to the computing world for a generation of programmers and engineers.

Overview

The ASR-33, an acronym for Automatic Send-Receive, was a electromechanical device designed for communication over standard Bell System lines. It was a refined version of the earlier Model 33, optimized for computer interaction rather than traditional telegraphy. Its introduction coincided with the rise of influential computer platforms like the DEC PDP-8 and PDP-11, with which it was frequently paired. The device's distinctive acoustic signature, a clattering sound from its solenoid-driven print mechanism, became a familiar sound in computer labs and research facilities worldwide.

Design and features

The ASR-33 was housed in a heavy, beige metal case with a keyboard resembling that of an electric typewriter. Its printing mechanism used a cylindrical typewheel that rotated and tilted to strike characters onto a roll of fanfold paper. A key feature was its integrated paper tape reader and punch, which used sprocket-fed punched tape for offline storage and program loading. The device communicated using the ASCII code at a standard speed of 10 characters per second (110 baud). Its electrical interface typically connected via a current loop to a computer's serial port, such as those on systems from Data General or IBM.

Operation and usage

In operation, the ASR-33 functioned as a combined terminal, printer, and tape drive. Users typed commands on the keyboard, which were transmitted to the host computer, with responses printed on the paper. The paper tape punch could create permanent copies of programs or data, while the tape reader could rapidly load them back into memory. This made it essential for bootstrapping systems and developing software on early networks like the ARPANET. Institutions such as the Massachusetts Institute of Technology, Stanford University, and Bell Labs relied heavily on these teleprinters for pioneering work in artificial intelligence and computer science.

Historical significance

The historical significance of the ASR-33 is profound, as it democratized access to computing. It was the primary interface for the first generation of time-sharing systems, such as those on the GE-600 series and the UNIX operating system developed at Bell Labs. Its use on the ARPANET, the precursor to the Internet, established the model for interactive, text-based computing. The device influenced the design of later video display terminals and cemented the QWERTY keyboard layout as the standard for computer input. Its reliability and simplicity made it a cornerstone of the computing revolution of the 1960s and 1970s.

Technical specifications

The ASR-33 operated on the 5-bit Baudot code or, more commonly for computing, the 7-bit ASCII code with one parity bit. Its print mechanism offered a 72-character line width at the standard speed of 10 characters per second. The paper tape reader could read tape at 10 characters per second, while the punch operated at the same speed. It required a 120-volt AC power supply and used a 20 milliampere current loop for data transmission. The machine was notably robust, with a design philosophy emphasizing mechanical durability over electronic complexity, a hallmark of Teletype Corporation engineering from its roots in the Morkrum company.

Category:Teleprinters Category:Computer peripherals Category:American inventions