IBM 7868-047 Modems

Peter Coghlan cctech at
Mon Nov 3 03:20:31 CST 2014

>Does anyone have any info or familiarity with this modem? I know some other
>IBM LL modems could work over PTSN but had to be set in the right mode. Can
>this be done for these modems? Also does anyone know if these modems will
>accept standard Hayes AT commands? Or just the IBM command set? Which brings
>me to my next question what is the IBM command set?
>Any documentation or guidance is very much appreciated. I would love to get
>these guys up and running!

Unfortunately I don't have anything on these particular modems.  However, I do
have a couple of leased line modems (Nokia I think) which were abandoned by the
telecoms provider when the lines were ceased.  They were both set up to be
clocked from the telco end, presumably to stop the customer from changing the
clock speed to see if their line would work at a faster rate than they were
paying for.

Amazingly, one had a little plastic folder glued on the top containing a
booklet showing how to run the self tests and what the jumpers did so I was
able to change the settings on one of them to provide the required clocking.
When I joined them with two pairs of wires, they seemed happy enough to talk
to each other.

If you want to use your modems on the PSTN, the first thing to check is whether
they require a single pair connection between them or two pairs.  My ones
have RJ11 type connectors which might give the impression that only a single
pair is required but two of the pairs are actually used, one for transmit and
the other for receive.

It is also possible that your modems are synchronous only which will be a
problem if you want to talk to asynchronous only modems.

Peter Coghlan.

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