7
6. Working Without A Telephone Line.
6.1 Telephone line outputs.
•
POST 1: Equipment connected to this terminal will use the PSTN line
connected to ‘POST 2’ while it exists, and swap to the GSM network in
the event of a failure.
6.2. GSM converter line characteristics.
The GSM line that substitutes the conventional PSTN line is almost
identically to a normal telephone line.
The GSM line complies with the tbr-21 requirements.
6.3. Outgoing GSM telephone operation.
The GSM converter will wait until a call comes through ‘POST1’.
Once a call is detected, the GSM converter will call the number dialed
through its GSM module. Call Tones must be DTMF.
Once the communication has started the GSM converter will link the audio
between the equipment and the receiver.
Any call through the GSM line will finish when the equipment that started
the call hangs up. The GSM converter will then wait for another call.
6.4. Restoring of PSTN line.
The GSM converter will continually check the PSTN line status to detect
if it is restored or not. If the correct voltage is detected on the telephone
line, it will wait a short period and then try the line again, checking the
voltage and the tones frequency.
If the line is tested as ok continually for 60 seconds, outgoing calls will be
routed back over the PSTN line again.
