Modems and external dialers.

[Ethan Dicks]

On Wed, Jun 5, 2019 at 11:45 AM Grant Taylor via cctalk
<cctalk at classiccmp.org> wrote:
> On 6/5/19 9:58 AM, Ethan Dicks via cctalk wrote:
> > Not quite... the USD 801 ACU I keep mentioning supported dialing using
> > either RS-232 or RS-366 over the same physical port.  It was a flexible
> > device that would work with a parallel dialing controller like the DEC
> > DN11 or by just using a second serial port from your host.
>
> Okay.  Now I'm even more confused.  I'll have to go back and re-read
> some of the links you shared.  I'd swear that the brochure mentioned 1 x
> RS-232 + 1 x RS-366 -or- 2 x RS-232 port requirement on hosts.

I agree with what that brochure says.  The 801 ACU + Modem needed
either RS-366 + 1 x RS-232 or 2 x RS-232 depending on what you had to
drive it.  It was more flexible than some other ACUs that only
provided one type of physical connection.

The DN11 connects to the 801 ACU via RS-366.  In conjunction with
that, one of your PDP-11/VAX RS-232 serial ports was used for the
modem.

For the COMBOARD example, the COMBOARD itself provided a sync serial
port, not a serial port of the VAX you were on, to talk to the sync
modem, _but_ one of the VAX ports _was_ used to drive the 801 ACU.

> > The other connector was a handset connector for a standard US telephone
> > (narrow 4p4c jack).

The rest of my message was about the VICmodem and nothing to do with an 801 ACU.

> So the phone played an active role in modem communications.  At least in
> so far as it converted the purely audio from the modem to telephony used
> by the PSTN.

Yes.

> Intriguing.  I've never done much with anything other than 9600 or
> 115200 for terminal connections to equipment to configure & manage said
> equipment.

My first 9600 connection to a machine was a local terminal on a VAX at
work.  My own gear didn't go that fast in those days.  I'm trying to
remember if I got a (new) Amiga 1000 first or a (used) PDP-11/23
first, but one of those two was what I could finally use to go that
fast at home.  My fastest modem for a long while was a borrowed 1200
baud modem for calling into work/school.

My first modems were the aforementioned VICmodem (300 baud) and a
suitcase-sized 110 baud "DataSet" mounted into the bottom of an ASR33.

-ethan