Simultaneously the PBX tells the voicemail system ( through signaling link D ) that the call it is forwarding to voice - mail is for Fred at extension 2345 .
It does this because PBXs are generally programmed to forward busy or unanswered calls to another extension .
The PBXs tells the voicemail system ( through signaling link D ) that the call PBXs is forwarding to voice - mail is for Fred at extension 2345 .
It does this because PBXs are generally programmed to forward busy or unanswered calls to another extension .