Cheap Analog PBX was: RE: Google, Wikipedia directly on ASCII terminal?

Ethan Dicks ethan.dicks at
Tue Jan 16 22:05:02 CST 2018

On Tue, Jan 16, 2018 at 6:59 PM, Anders Nelson via cctalk
<cctalk at> wrote:
> Silvertel makes POTS line interfaces (SLICs) that work on 3.3v or 5v
> supplies. They do all the high voltage generation and impedance wizardry on
> the POTS side, then expose audio in/out and simple control lines.

I've worked with early versions of SLIC - circa 1990... even then,
they packed enormous amounts of telco stuff in a small package.

One place I worked for made a 2-line telco simulator product - the
primary use was testing auto-dialling software to replicate various
fault conditions.

> To complete the picture you'd have to generate the tones and decode the
> numbers but that's it I'm guessing.
> Practical? No. Awesome? Yes.

We did that with an 8749 (MCS-48) microcontroller.  By dialling
different phone numbers from one of the stations, the MCU would
complete a connection or play a busy or fast busy signal.


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