Gavin Jackson wrote:

> EF7910PL by SGS-Thomson
> "A single chip modem capable of receiving and
> transmitting in full duplex, half duplex or simplex  ... etc.

  Err, yes.  Depends on what you mean by "modem".  The venerable 7910
with its one-watt power consumption and dual +/-5V power supplies is
indeed a modem chip.  What it is NOT, is a TELEPHONE modem for which it
requires hybrid, isolation, line control and dialling (either DTMF or
impulse) and ring detection circuitry to be ADDED.  The digital
interface is of course raw data at TTL levels.  You want smarts, you add
them too.

  Not that it matters for alarm diallers, but the 1200 baud is only
half-duplex on a 2-wire circuit, too.

  Note my comment on power consumption - OVER one watt.  Runs hot!

  Cheers,
        Paul B.