Multi Address Appearance on OpenStage
00.00.2007
I 7
Functional Overview
Motivation
A telephone is normally associated with a directory number, or in general, with SIP: an AoR. This
number is used for placing calls to this telephone and for displaying the telephone's, resp. user's
identity when placing calls to another party. This number is also used when more than one call
appearance is supported due to additional features, like call waiting.
A keyset is a telephone that is associated with more than one number - this allows a given telephone to
act on behalf of different phone numbers, or users. Just like with traditional telephony systems, people
sometimes refer to lines instead of numbers, hence keyset phones are also referred to as multiline
phones. The main line, i.e. the line/directory number for the user associated with a given physical
telephone, is called primary line, whereas all other lines that can be handled on other phones are
called secondary lines. Call Log and MWI are working for the primary line only and not for secondary
lines. Sharing of lines is possible, but, as mentioned before, this is not in the focus of this document.
At any given time, one telephone can handle only one call appearance for connecting to the handset,
and the same applies to keyset / multiline telephones. Also for keyset telephones, features like call
waiting can increase the number of call appearances that can be handled, but on a keyset telephone,
these appearances may refer to different lines / numbers / users. The programmable feature keys are
used for handling the lines and their respective call appearances, supported by the associated LEDs
reflecting the line/call status. The number of lines that can be configured depends on the phone model.
This feature can be used for the following use cases, amongst others:
Address multiple users at one phone
Enhanced Call Hold Scenarios
Allow more than two incoming calls at one phone
This feature can not be used for the following use cases, amongst others:
MLA. If the line is configured at more than one phone, incoming calls are sent to the last
registered device.
Line status observation. If the same line is configured at more than one phone, the line status
is not presented at these phones.
Depending on the selected system, a specific set of additional features for handling call appearances is
available (e.g. placing calls on hold).
Similar features are named Bridged Line Appearance (BLA) and Shared Call Appearance (SCA).
