This feature enables a phone to connect silently to a call between two other parties. It has 3 modes that define whether the monitoring phone could be heard by other two.

Precondition: Extension A has a connected call with Extension B

On Extension C (supervisor) which has Monitoring key configured, press the Monitoring key and enter Extension A.

By default it connects in spy mode (DTMF:4). Extension C shall be listening the call between A and B and cannot be heard by them.

Pressing 5 on Extension C changes to whisper mode. Extension A will be hearing Extension C now. Extension B does not hear Extension B.

Pressing 6 on Extension C changes to barge mode. All three parties can hear each other in this mode.