Teletype Corporation
ASR-33 teleprinter

    This is perhaps the first impression nascent programmers got of computing (at least in my generation). These sturdy devices provided hardcopy output and a keyboard for input in the same enclosure.

    Operation of these machines was almost purely mechanical; the only parts that could be considered "electronic" were a (fairly simple) power supply, the switches in the keyboard (8 of them, seven for the character proper and one for parity, operated by cams and levers to produce the ASCII code for the depressed key), and the switches (again 8) in the tape reader.

    Speed of communication was 110 bits per second, or approximately 10 characters per second (about 100 words/minute). The keys had to be depressed about a half-inch before a character would be generated. The ASR-33 was only capable of rendering text in upper case and, thus, possibly served as the originator of the bad programmers' habit of only using capital letters. The decision to make the unit mono- case was based on a cost/ market choice.

    True ASR-33s (ASR standing for "Automatic Send and Receive") had integral paper tape readers and punches; the punch being completely mechanical in design, the reader using open contact switches. Both reader and punch were controllable from a remote location. On many minicomputer installations, ASR-33s were fitted with "Reader Run" relays to control the reader (rather than using Xon/Xoff). These relays, in turn, were activated by a dedicated line from the computer.

    The reader resides just to the left of the keyboard; the punch sits behind the reader. The punch is connected mechanically to the type selection bars in the main unit and, since it was an option, is disconnectable (with work). The reader is electrically connected to the transmission mechanism.

    A version of the machine was available that didn't include either the reader or the punch. These machines were known as KSR-33s (KSR being an abbreviation of "Keyboard Send and Receive"). There was even a variant that lacked any input capability, and hence was known as the RO-33 (for "Receive Only").

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