Teletype 43

Philipp Hachtmann hachti at
Wed May 24 05:45:11 CDT 2017

On 23.05.2017 03:41, Ethan Dicks via cctalk wrote:
> No eye-rolling here.  Nice find!
Here the same. Perhaps not the most wanted device - but... better have 
than need...

>>> I got home last night, and the unit fires up and works (well, in local mode.  Docs claim
>>> it is rs232 out the back, but could not coax anything from my PC to it yet),
> Do you have a "traffic light"?  I find them invaluable for diagnosing
> handshaking and TxD/RxD swaps.
The first thing I thought of. Everybody needs one. And 25/9-Adapters in 
both directions, null modem cables and gender changers - then you get 
everything running. Ok, add some sub d connectors to make weirdly wired 
adapters if nothing helps.

>> Does your PC have real RS232?  A lot of "RS232" ports are serial ports, but not with correct
>> RS232 levels.  If you have "TTL RS232" [sic] it won't work with an actual RS232 port.
I don't think that it's reasonable to check this problem first. Of 
course, can happen. But more likely you have a null modem problem.

Keep in mind that "TXD" is the output of a DTE (Data Terminal 
Equipment). TXD is therefore the input (!) of a DCE (Data Communication 
Equipment aka modem).
PC RS-232 ports send on TXD because they consider themselves to be a 
terminal. And a teletype IS actually a terminal. So you would need to at 
least cross wires 2 and 3 (RXD/TXD) using a Null modem. If you want 
hardware handshake, the same applies to DTR and CTS.

Good luck :-)

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