Yealink SIP-T29G User Manual page 159

Advanced Phone Features
You can use SCA feature to share an extension which can be registered on two or more
IP phones at the same time. The shared line is indicated by a different line icon.
In the following figure, the first line is private and the second line is shared:
If two phones share a line, an incoming call to this extension will cause both phones to
ring simultaneously. The incoming call can be answered on either phone but not both.
This feature is very useful in the boss and secretary scenario. For example, the secretary
can share the boss's extension on her phone. When there is an incoming call to the
extension of the boss, both the phones of the boss and the secretary will ring
simultaneously. Either the boss or the secretary can answer the call. Calls on the shared
line can be placed on hold, barged in or retrieved from another shared phone.
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