Call Hold - Yealink SIP-T54S Administrator's Manual

Select the desired refresher from the pull-down list of Session Refresher.
5.
Click Confirm to accept the change.
6.

Call Hold

Call hold provides a service of placing an active call on hold. The purpose of call hold is to
pause activity on the existing call so that you can use the phone for another task (e.g., to place
or receive another call).
When a call is placed on hold, the IP phones send an INVITE request with HOLD SDP to request
remote parties to stop sending media and to inform them that they are being held. IP phones
support two call hold methods, one is
to sendonly, recvonly or inactive (e.g., a=sendonly). The other is
(connection addresses for the media streams) in the SDP to zero (e.g., c=0.0.0.0).
Call hold tone allows IP phones to play a warning tone at regular intervals when there is a call
on hold. The warning tone is played through the speakerphone.
RFC 3264, which sets the "a" (media attribute) in the SDP
Configuring Basic Features
RFC 2543, which sets the "c"
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