An intercom line is
a dedicated two-way audio path between two phones. Cisco Unified CME supports
intercom functionality for one-way and press-to-answer voice connections using
a dedicated pair of intercom directory numbers on two phones that speed-dial
When an intercom
speed dial button is pressed, a call is speed-dialed to the directory that is
the other half of the dedicated pair. The called phone automatically answers
the call in speaker-phone mode with mute activated, providing a one-way voice
path from the initiator to the recipient. A beep is sounded when the call is
auto-answered to alert the recipient to the incoming call. To respond to the
intercom call and open a two-way voice path, the recipient deactivates the mute
function by pressing the Mute button or, on phones such as the Cisco Unified IP
Phone 7910, lifting the handset.
In Cisco CME 3.2.1
and later versions, you can deactivate the speaker-mute function on intercom
calls. For example, if phone user 1 makes an intercom call to phone user 2,
both users hear each other on connection when no-mute is configured. The
benefit is that people who receive intercom calls can be heard without them
having to disable the mute function. The disadvantage is that nearby background
sounds and conversations can be heard the moment a person receives an intercom
call, regardless of whether they are ready to take a call or not.
cannot be used in shared-line configurations. If a directory number is
configured for intercom operation, it must be associated with one IP phone
only. The intercom attribute causes an IP phone line to operate as an autodial
line for outbound calls and as an autoanswer-with-mute line for inbound calls.
shows an intercom between a receptionist and a manager.
To prevent an
unauthorized phone from dialing an intercom line (and creating a situation in
which a phone automatically answers a nonintercom call), you can assign the
intercom a directory number that includes an alphabetic character. No one can
dial the alphabetic character from a normal phone, but the phone at the other
end of the intercom can be configured to dial the number that contains the
alphabetic character through the Cisco Unified CME router. For example, the
intercom ephone-dns in
are assigned numbers with alphabetic characters so that only the receptionist
can call the manager on his or her intercom line, and no one except the manager
can call the receptionist on his or her intercom line.
requires the configuration of two ephone-dns, one each on a separate phone.