page_title: Teletype Model 33
section_title: Related machines
hierarchical_section_title: Teletype Model 33 / Related machines
caption_attribution_description: English: ASR 32 Telex machine. Note three row keyboard and five level paper tape. Author's Flickr description: "Upgraded this photo with one from a real camera instead of a camera phone on June 12, 2010. Enjoy. This machine is a very clean example of increasingly rare technology from the 1950s, through 1970s. I'm sure there are still some of these in use in odd locations around the world. Surprisingly, as best as I can determine, the TWX network still exists and is used.This particular machine was used by a furniture store to order stock."The paper tape supply reel is at the upper left; the tape is lying on top of the punch cover. The tape reader is at lower left. The panel to the right of the keyboard has a rotary telephone dial for connecting the machine to various destinations via the TWX network. Printing paper is supplied from an 8.44 inch wide roll, visible top center, and is fed through the printer mechanism with rubber pinch rollers. This machine is missing the trim cover plate on the front of the console.
context_page_description: The Teletype Model 33 is an electromechanical teleprinter designed for light-duty office use. It is less rugged and less expensive than earlier Teletype machines. The Teletype Corporation introduced the Model 33 as a commercial product in 1963 after being originally designed for the US Navy. There are three versions of the Model 33:
  the Model 33 ASR, which has a built-in eight-hole punched tape reader and tape punch;
  the Model 33 KSR, which lacks the paper tape reader and punch;
  the Model 33 RO which has neither a keyboard nor a reader/punch.
  The Model 33 was one of the first products to employ the newly standardized ASCII code. A companion Model 32 used the more established five-bit Baudot code. Because of its low price and ASCII-compatibility, the Model 33 was widely used with early minicomputers.
context_section_description: The Model 32 line used the same mechanism and looked identical, except for having a three-row keyboard and, on the ASR model, a five-hole paper tape reader and punch, both appropriate for Baudot code.
  Teletype also introduced a more expensive ASCII Model 35 for heavy duty use, whose printer mechanism was based on the older, rugged Model 28. The basic Model 35 was mounted in a light gray console that matched the width of the Model 33, while the Model 35 ASR with eight-hole mechanical tape punch and reader was installed in a console about twice as wide. The tape reader was mounted separately from the printer-punch mechanism on the left side of the console and behind it was a tray for storing a manual, sheets of paper, or other miscellanea. To the right of the keyboard was a panel that could optionally house a rotary dial or Touch-Tone pushbuttons for dialing a connection to a network via telephone lines. The printer cover in later units also featured sound deadening materials, making the Model 35 somewhat quieter than the Model 33 while printing and punching paper tapes. All versions of the Model 35 had a copy holder on the printer cover, making it more convenient for the operator when transcribing written material.
  Teletype model 35 is mentioned as being used in "Experiment One", in the first RFC, RFC1. The model 35 was used as terminals for the minicomputers and IMPs to send and receive text messages over the very early ARPANET, that later evolved into the internet.
  The Model 38 (ASR-38) was constructed similar to and had all the typing capabilities of a Model 33 ASR with additional features. A two-color ribbon and ASCII control codes allowed automatic switching between red and black output while printing. An extended keyboard and typewheel supported upper- and lower-case printing with some additional special characters. A wider pin-feed platen and typing mechanism allowed printing 132 columns fan-fold paper making its output similar to the 132-column page size of the then industry standard IBM 1403 model printers.
  More expensive Teletype systems used photo readers that used light sensors to detect the presence or absence of punched holes in the tape. These could work at much higher speeds (hundreds of characters per second). More sophisticated punches were also available that could run at somewhat higher speeds; Teletype's DRPE punch could operate at speeds up to 240 characters per second.
caption: A Model 32 used for Telex service. Note the three-row keyboard and narrower, five-hole paper tape.
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