4 Jun
2019
4 Jun
'19
7:31 p.m.
On Tue, Jun 4, 2019 at 9:45 PM Grant Taylor via cctalk
<cctalk at classiccmp.org> wrote:
Does anyone have any experience working with modems
that didn't include
internal / auto dialers?
Yes. I used to make and sell sync serial protocol engines (COMBOARDs)
that often were used to dial up an IBM Mainframe. Sync modems of the
80s often did not have built-in auto-diallers.
Here's one we used to use, a Motorola UDS 801 ACU (Automatic Call Unit).
http://nwrusa.com/Networking?product_id=17371
https://www.arcelect.com/801_autodialer.PDF
I still have one on a shelf in the basement.
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?
Yes (though the USD 801 ACU could be controlled by a parallel port
_or_ a serial port) In our case, our product had a sync serial port
to talk the the Host (implemented with either a COM 5025 or a Z8530).
To run the 801 ACU, we soaked up an async port on the VAX as well.
Sometime after 1990, I added V.25bis support to our product so we
could control autodialers of the day.
-ethan