Modems and external dialers.

[Ethan Dicks]

On Tue, Jun 4, 2019 at 10:50 PM Tony Duell via cctalk
<cctalk at classiccmp.org> wrote:
> On Wed, Jun 5, 2019 at 2:45 AM Grant Taylor via cctalk
> <cctalk at classiccmp.org> wrote:
> >
> > Does anyone have any experience working with modems that didn't include
> > internal / auto dialers?
>
> It wasn't normally a serial port. It was on a DB25 connector, and used
> the same voltages as RS232...

The UDS 801 ACU supported either serial or parallel over the same DB25
connector.

> ...but the number to dial was sent a digit
> at a time over 4 lines (obvious BCD code, I am not sure if the other
> 6 possibilities were used), along with a digit strobe line, various status
> lines, etc.

Yes.   I think some of the other 6 codes were used for other dial
symbols (',' for pause, for example) but I didn't quickly find a
definitive list.

> The standard was, I think, RS366, but I have never managed to find
> any real information on it.

Yes.  RS366 was the standard for parallel-driven autodiallers, later
EIA-366.  Also, V.25 is an autodialler standard.

There's some implementation detail in the DEC DN11 docs on Bitsavers.

-ethan