Teletype services

Chris Elmquist chrise at
Thu Nov 5 18:07:26 CST 2015

On Thursday (11/05/2015 at 10:59AM -0800), John Ball wrote:
> I've been trying for the past week to verify that telephony on my teletype
> machine (model 33) is functioning properly but the biggest hurdle I am
> running into is I have nothing to easily dial into. Everyone I know off hand
> either don't have a modem anymore or theirs is a Winmodem which won't work.
> There's only one phone line into the residence here and those bluetooth to
> cellular POTS bridges are too lossy to make do and connect to a machine
> here. There is that youtube video of the model 37 apparently connecting to a
> system at the Living Computer Museum in 2013 (MikoF6KZjm0) where they dialed
> into a BBS I've never seen listed anywhere but the number listed no longer
> seems to work and in the description it states the service is no longer
> available. What other public systems are still out there that will work this
> speed or possibly better yet, is there anyone out there willing to try a
> teletype-to-teletype conversation?

If you have a "Smart Modem" (ie, stand alone unit with serial port)
you can connect it to the modem in the Teletype with a battery-- like,
a 9V battery-- in series with the phone line between the two.   Then you
use the Teletype modem to place a call to any random number and command
the Smart Modem to go off-hook with "ATA".   This will cause it to
generate answer tones and the Teletype originate modem will "connect"
and off you go.

You don't need a ring generator or any ring voltage on the line since you
can manually command the Smart Modem at the answer end to answer with the
"ATA" command.

I pretty much ignored "WinModems" in the day but I would think that
if they can do answer mode, this approach would work with one of those
as well.  Open the terminal app on the Windows box in which this WinModem
is installed and simply enter "ATA" to cause it to go off-hook in answer
mode.  If the 9V battery is in series with the line to the modem in the
Teletype, you should be good.  There might be polarity issues so reverse
the battery if it doesn't work the first time.

Chris Elmquist

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