Ancient Modems (was Re: Who says familiy activities are extinct? ^_^) - test-drb@ccmp.vtda.org

18 Jun 1999

--- Tony Duell &lt;ard(a)p850ug1.demon.co.uk&gt; wrote:
...
  Date: Fri, 18 Jun 1999 19:53:11 +0100 (BST)
 Reply-to: classiccmp(a)u.washington.edu
 From: ard(a)p850ug1.demon.co.uk (Tony Duell)
 To: "Discussion re-collecting of classic computers"
 &lt;classiccmp(a)u.washington.edu&gt;
 Subject: Re: Who says familiy activities are extinct? ^_^

 Yeah, those are what they are, LDSsomethings, with 4-wire connections.
 Do those need AT commands to set up or similar, or do they just
 stay in data mode all the time?  
 AT commands? Surely you jest. Have you looked inside (take off the feet 
 and slide the cover backwards). It's all simple analogue chips and 
 discretes inside. No microcontroller, no command language.

 Once you've connected them up, they behave like a long RS232 cable (data 
 leads only). Squirt data in one end, get it out the other. 
I missed the top of this, but I think this thread is about some older
Modems, Motorola UDS's, yes?  If I read what's gone on correctly, a
four-wire device is for leased lines.  You didn't even dial them.  You
just hooked them up and squirt away.

Older two-wire modems, especially those that move sync data, are also 
lacking in dialing facilities.  There was a seperate box that you routed
the phone line through and sent commands via serial or parallel port to
make the external box do the dialling.  We used one when we were making
sync comm equipment for VAXen more than ten years ago.  I forget the first
part of the designation, but it was a mumble-mumble 850 autodialler, the
standard.  Much later, ANSI invented an autodial protocol, V.25, IIRC.  I
have a Motorola 2400 sync/async V.25 _and_ Hayes modem from those days. 
It would work like a regular modem over a regular serial port, or if you
used it in sync mode, you could send it V.25 autodial commands.  One of
my jobs back then was to retrofit the V.25 command set into our product.

It was pretty cool when it all worked, but cool is a relative thing when
you are working with stone knives and bearskins.

-ethan

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