TELETYPE MODEL 32 PAGE PRINTER

Model 32 Type-Wheel Page Printer
M32-ASR-1-400w.jpg

Standard Models: 32-ASR, 32-KSR, and 32-RO
Military Models: ??
Relatives: ??
Manufactured: 19??-19??
Units Produced: ??
Units Remaining: ?? (estimated)
Dimensions (inches): ??
Weight (pounds): ??

Keyboard: 3-row with gray plastic keycaps
Code: 5-level baudot (ustty or ita2) at ?? wpm (?? baud)
Interface: 20-mA current loop (@48VDC typical?)
Full- or Half-Duplex
Motors: 115-VAC Synchronous
Options: Telex CCU...??

The Teletype Corp Model 32 was offered in Receive-Only (RO), Keyboard-Send-Receive (KSR), and Auto-Send-Receive (ASR) versions. Shown above, is a clean Telex M32-ASR belonging to Dave Ross. The M32 is a ...

(need more poop here)....

Most Model 32 machines seem to be Telex units -- they have a rotary dialer and four buttons at the front. According to my manual this CCU is for what they called "Circuit-Switching-Service," and the buttons are labelled: START, DIAL, LOCAL, and CONN(STOP), or possibly labelled: REQUEST, CONN, LCL, and DISCONN. As I understand it, Telex is a dialup service that uses DC signaling (no modem) and is 50-baud baudot. Telex was a service Western Union brought to the US starting in 1958, after it had been used in Europe for a long time -- the 50-baud was a European standard. I belive that Telex machines had some sort of line-interface box in the stand.

Here's part of the description of the four-button "Circuit-Switching" (Telex) CCU: "The dialer is a conventional telephone type...contacts open and close to send dialing pulses...in the idle condition, there is a positive current of 0.005 ampere in the telegraph loop. When the calling station operator depresses the START button, it causes the shunting of a major portion of the loop resistance, and the loop current increases to 0.060 ampere. The START button must be held while switching apparatus in the telegraph exchange is made available. When the circuit is ready, the telegraph exchange interrupts the 0.060 ampere loop current for about 0.025 second. This "proceed-to-dial" signal causes the DIAL lamp to illuminate at the calling station, and it locks the shunt to the loop resistance so that the operator may release the START button and proceed to dial the number of the called station...When dialing is complete, the exchange furnishes the connection and signifies this by reversing the telegraph loop current from positive to negative, which causes the typing unit motor to start and the CONN light to illuminate. Message transmission can now be exchanged between the connected teletypewriters. The line signals are 0.060 ampere marking and zero current spacing."

This is most certainly not a telephone line connection. And while a 60-mil loop is used for communication, it cannot simply connect to a conventional (neutral or polar) current loop. It seems that the "telegraph exchange" would need to be emulated to provide a true "Telex" interface to this unit -- this could be done with a microcontroller, if someone was really motivated. But it would be easier to tap into the internal 20-mil current loop in the CCU at the selector driver board.


No, it's not an ascii 33, it's a baudot 32, as indicated by a 3-row (not 4-row) keyboard. Most 32 machines seem to be Telex units, which had the rotary dialer and four pushbuttons -- if it had six buttons, or a touch-tone dialer, it will be a TWX machine that has a modem. But I don't know if any 32 units were used with TWX or not. The early TWX used baudot and M15 machines, but later changed to ascii and M33 machines. M32-ASR-2a.jpg

This is the CCU for the Telex version. I belive this pic, and the next few, are from Dave Wimsatt's M32. I don't think the red/black ribbon is correct -- that would require a dual-color ribbon shift mechanism. M32-ASR-2c.jpg

There's a lot more electronics than earlier machines. M32-ASR-2d.jpg

Function options installed in this area. M32-ASR-2e.jpg

The blue plastic paddlewheel is the "answer-back" drum -- you break off tines (or not) to code the characters, and program it with an ID string for your machine. The drum code can be read remotely. M32-ASR-2f.jpg

This is the Telex dialer -- it does not dial phone numbers, but rather some sort of station ID that is selected via a central Telex switching office. M32-ASR-2h.jpg

Telex machines used a special wired network, and a polarity-reversing current loop. To hook one up today, you either need to build a special box to emulate a Telex central office, or tap into the internal 20-mil current loop in the CCU at the selector driver board. M32-ASR-3.jpg

This 32 is a private-wire 20-mil current loop machine, which is easy to interface to RS-232, using a converter circuit. M32-ASR-6.jpg