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Using an ASR 33 Teletype with IBM PC

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  Using an ASR 33 Teletype with IBM PC by Bill Degnan - 06/14/2011 20:56
There is a socketed shunt module on the bottom right of the original IBM async board, just pull it out and re-insert upside down (so the dot is pointing down) for current loop. If you're going to use slot 8 of an IBM PC or XT a jumper is required on connector J13. Why I don't know off-hand.



Plug a regular-old EIA connector into the serial card in the back. The serial connector pins you need to connect to the teletype are are:


pin 9 = + transmit current loop data
pin 11 = - transmit current loop data

pin 18 = + receive current loop data
pin 25 = - receive current loop data

[pin 25 is the bottom right (bottom = row of 12 pins)]


Then connect to ASR 33:


Transmitted data return (-) attaches to terminal strip screw 6 or "number 2 connector" #7

Received data return (-) attaches to terminal strip screw 3 or num 2 connector #5

Transmitted data send (+): Terminal Strip 7, #2 connector 8

received data send (+): Term strip 4, #2 connector #6.


If the tty stops chattering you at least have a current loop. You'll need some sort of terminal program just like you'd use with an RS232 terminal connection, but you will need to use 110b, etc.

Source - Paraphrase from IBM Technical Reference Manual volume 2



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  Using ASR 33 as IBM PC Console by Bill Degnan - 02/08/2013 09:51
If you have an IBM Asynchronous Communications Adapter configured for current loop, then you can in theory use a teletype as the console to interface with the PC.

MODE COM1:110,N,8,1
CTTY COM1

[I need to try this myself, if anyone reads this post and has corrections please advise.]

--------

Using the software that came with the IBM Asynchronous Communications adapter it should also be possible to make a direct connection to the teletype via the serial port and use to upload ASCII into a file (while papertape is being read in by the TTY reader)

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  Cable for IBM PC to Teletype by Bill Degnan - 02/11/2013 22:09
In addition to connecting pins 9,11,18,25 from the async card to the teletype, Chuck(G) of vintage-computer.com forums says "...the PC still pays attention to DSR, DTR, RTS and CTS. So you still have to jumper 4-5 and 6-8-20 on the PC DB25. ..

Request-to-send -> Clear-to-send (pin 4 to pin 5)
Data Set Ready -> Carrier detect -> Data terminal ready (pin 6 to 8 to 20)"

Thanks Chuck!

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  IBM Async Card Current Loop Jumper by Bill Degnan - 02/19/2013 21:02
Photo of the jumper in the "current loop" position.

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