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5-210 41-001160-01, Rev 00, Release 2.3
IP Phone Administrator Guide
Bridged Line Appearance (BLA)
A SIP bridge line appearance (BLA) on the IP phones allows multiple devices to
share a single directory address (DA).
For example, people working at a technical support department could be located
in different places. If their desktop phones are configured for BLA DA, when
customer calls come in, all the phones with the BLA DA would ring but the call
can only be answered by one of them.
Once the call is answered, the rest of the phones reflect the status of the call. If the
call was put on "hold" by the original recipient, any one from the group can pick
up the call.
You can apply BLA on the IP phones as follows:
• As a single BLA group - One BLA DA is shared among multiple phones.
Only one phone at a time can pick up an incoming call or initiate an outgoing
call on the BLA DA. All phones reflect the usage of the BLA DA. If the call is
put on "hold", any one from the group can pick up the "held" call.
• As a multiple BLA group - On one single phone, multiple BLA DA can be
associated with different line appearances. Every BLA DA is independent
from each other and follows the same rules as "a single BLA group".
• As multiple instances of a BLA DA - A "x-line-id" parameter was defined in
draft-anil-sipping-bla-02.txt to present the incoming call to or place an
outgoing call on the specified line appearance instance. The parameter is
carried in "Alert-Info" header field over the request-URI (INVITE e.g.) or in
the NOTIFY messages to report the status of a dialog.
BLA DA can be configured on a global basis or on a per-line basis on the IP
phones using the Aastra Web UI or the configuration files.
Note: This feature is dependent on the IP telephony system to which the
IP phone is registered and according to draft-anil-sipping-bla-02.txt.