Re: Telephone compatibility


Ian Stirling wrote:

> > Does anyone know whether the Voice dialer security system found in
> > Alarm systems designed for the US is compatibile with that for Austria
> > or for the rest of Europe.
>
> Probably not.
> Dialtones and stuff vary quite widely over europe.

Alarm systems generally do not detect dialtone; they check line voltage
to determine if the line is cut, and they have a seize relay to ensure
that they can interrupt any call in progress. They also do not
generally use modem chipsets (there are exceptions to both rules but
mass-market appliances tend to use simple DTMF generators/recognizers).
The system decides if communications startup was successful by waiting
for a handshake tone from the central station, and a kissoff tone after
the report session is finished.

Audio verification systems start by sending a DTMF report in the method
described, then flag the central station to switch the call through to
an operator after kissoff rather than just hanging up.

Sometimes there are special regulatory rules that require the alarm
system to monitor and recognize PSTN-provided call progress tones, but
this is not the norm.

.