Modems and external dialers.

[Tony Duell]

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?

Only from the side of the things that talked to them, like the HP11284 interface
for the HP9830
>
> They came up in a conversation in a newsgroup and I realized that I know
> of them, but know virtually nothing about them.
>
> I think they were separate devices, which probably means that they
> likely had separate serial ports to talk to each of them.  Did they
> support some sort of pass through?  Or did they really require two
> serial ports on the host?

It wasn't normally a serial port. It was on a DB25 connector, and used
the same voltages as RS232, 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.

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

-tony