Simulated telephone

Richard Cini rich.cini at
Wed Aug 25 17:53:27 CDT 2010

For my BBS project using the N8VEM, I used a TalkSwitch PBX. Downside to
that is it's Touch-Tone only. I've also used a decommissioned Panasonic PBX
(I forget the model number) with 24 station lines and 8 CO lines. I used
this setup with everything from the PMMI modem on my IMSAI to modems of
Commodore and Apple vintage. Works like a charm.

On 8/24/10 3:08 PM, "Michael Lee" <mikelee at> wrote:

> PBX Simulators, different makes and models out there and while currently
> it appears the ones on ebay cost more than it would new, they can
> usually be obtained for a reasonable cost.  The models I've used have a
> handful of POTS jacks, 4 or 8 of them, and it gives basic tone and dial,
> you just dial 1 for POTS 1, etc.
> On 8/24/2010 10:51 AM, Jim Scheef wrote:
>> Hello all,
>> I would like to play^H^H^H^H use some of my vintage portables the way
>> they were intended. For example, the Radio Shack Model 100 and the HP
>> 110 Portable have 300bps internal modems. I have several other modems
>> thru which these machines could talk to a *NIX but I do not want to
>> pay for multiple phone lines in my home. How can I simulate a POTS
>> connection between these modems? I don't need a dial tone or ringing,
>> etc., as I can just tell one machine to connect and the other to
>> answer. Way back I heard that a few modems would work if the tip and
>> ring wires of the modems were crossed and connected, but most need
>> something more than that. Is there some simple circuit I could build?
>> Surely I'm not the first to want to avoid phone bills for such
>> play^H^H^H^H testing.
>> Jim


Rich Cini
Collector of Classic Computers
Build Master and lead engineer, Altair32 Emulator

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