Re; What to look for in a Model 33 Teletype - a newb's buyer's guide?

Fred Cisin cisin at
Fri Nov 21 15:57:13 CST 2014

On Fri, 21 Nov 2014, Noel Chiappa wrote:
> If you have a working UNIBUS PDP-11, there are still 20mA serial interfaces
> avalable for it.

If you have an ISA bus PC, there were 20mA serial interfaces available for
it.  The original IBM "Asynchronous Adapter" could be jumpered for 20mA.
While I don't have any handy right now (maybe in the shed?), they were
rather readily available.  IBM gave away one free with every 5160 around
here!  That was probably because they had more of them than could be
reasonably expected to sell before they dissolved, and because the 5160
had one slot that IBM did not want people using for anything else, and the
easiest way to prevent its use was to plug it up with a serial card.

The software to read a character on the serial card (20mA) and send it out
through another serial port (RS232) is reasonably trivial.
Therefore, a 5160 (or any other PC with ISA bus) could be converted into a
20mA to RS232 converter at negligible cost.

Grumpy Ol' Fred     		cisin at

More information about the cctech mailing list