14215700-IG, Edition 15.0
May 2020, Original document
422
Appendix A - Intercom (Push-To-Talk)
Using a Spectralink IP-DECT/Virtual IP-DECT Server, an auto-answer feature, intercom, is avail-
able, making it possible to use intercom and loudspeaker calls if numbers for intercom groups are
defined on the SIP PBX.
Activation of Intercom using Headers
If an INVITE with an Alert-Info header, a Call-Info header or an Answer-Mode header is received,
it is possible to make a Spectralink DECT Handset automatically answer the call, mute the micro-
phone and turn on speakerphone.
Note:
The reason for handling several headers for activating the Push-to-Talk feature is that dif-
ferent SIP PBXs have different default implementations.
The following list of headers will activate intercom (auto-answer) when sent from the SIPPBX to the
Spectralink IP-DECT/Virtual IP-DECT Server:
l Alert-Info: Auto Answer
l Alert-Info: info=alert-autoanswer
l Alert-Info: Ring Answer
l Alert-Info: info=RingAnswer
l Alert-Info: Intercom
l Alert-Info: info=intercom
l Call-Info: =\;answer-after=0
l Call-Info: ;answer-after=0
l Answer-Mode: Auto (This is according to RFC 5373)
Note:
The Alert-Info header can also be used to control external/internal ring pattern. This fea-
ture is not affected by the addition of the loudspeaker call feature.
The following Alert-Info headers can be used to enable internal ringing (external ringing
is default).
l Alert-Info: <internal>
l Alert-Info: <alert-internal>
l Alert-Info: internal
l Alert-Info: alert-internal
Spectralink IP-DECT Server 200/400/6500 and Virtual IP-DECT Server One Installation and Configuration Guide
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