Siemens hicom 150 e User Manual page 163

1.
Internal
2.
3.
Executing the feature
Press the Internal key (only necessary if automatic
trunk seizure is active).
Dial the internal station number of the telephone in
the room that you want to monitor.
Lift the handset; the LED on the Speaker key goes
out. Alternatively, leave the telephone in speaker-
phone mode.
General System Features
163