In the small and medium business market, legacy TDM-based PBXs are often configured with shared call appearance lines for incoming calls. Shared call appearance lines are lines that appear on multiple phones and deliver the following functionality:
Small and medium businesses using shared call appearance on their their existing TDM-based phone systems often request this capability when upgrading to a new phone system. Many medical, legal, and financial practices with one or more receptionists leverage the shared call appearance capability in their phone systems to answer calls centrally, and simplify the process of transferring calls from the reception area by placing the caller on hold and requesting another person to 'pick up the line on hold'.
With sipXcom, this capability is called Bridged Line Appearance (BLA) - the remainder of this document describes how to enable this feature with Polycom VVX Business Media and Polycom Soundpoint IP phones. sipXcom releases 14.04 and 14.10 have been used to validate BLA functionality in the following lab configuration:
Each phone has three appearances of a BLA-enabled 'Main Line' x300 on their phones. Incoming calls to the main line will ring the first available main line as follows:
The 'rollover' main line behavior only works properly when the same number of BLA-enabled lines appears on each phone. BLA lights will not appear in all cases when there is an asymmetrical number of BLA-enabled line appearances across the phones.
After x300 has been defined, go to Users->Phone section and click on the Shared button - this enables the BLA capability on the line.
Load the Polycom Firmware and Updater onto the sipXcom voice server. Assign each device file to the correct version (4.0.x or 4.1.7). Map the phones to the correct firmware versions in the Phones->Mac Address–>Firmware Version field - push the phone profiles.
Caution - BLA does not work properly with Polycom 4.1.8 and higher firmware loads on VVX phones and Polycom 4.0.6 and higher on Soundpoint IP phones. A 'ghost' line with red light appears on the phone answering the BLA-enabled line. This issue was resolved with Polycom 5.2.5 firmware released December 11, 2015 and verified with Sipxcom release 15.10.
Assign the personal line as the first line on each phone, and the BLA-enabled main line as the second line. For the BLA-enabled line on each phone, go to the Line->Registration section, and change the number of line keys on each phone to 3 from 1, and the Calls Per lLine Key from 24 to 1. This step is necessary for creating the roll-over effect on the main line.
Go the System->Six Proxy menu and disable the Enable for external calls Alert-Info options. This capability is normally used to map calls to specific call waiting types and (beep, ring, and silent) - Sipxproxy inserts Alert-info values and class fields in the SIP header when this option is enabled that informs the phones what ring types are used. With BLA lines and the Enable for External Calls Alert-Info option disabled, Sipxproxy will check each appearance of a BLA-enabled line on the phone whether it is available to handle an incoming call. With the Alert-info option enabled, Sipxproxy will not check each appearance of a BLA-enabled line on the phone. With the CallsperLineKey option set to 1, Sipxproxy will send subsequent calls to voicemail or the AA when the first main line is active and Alert-Info options are enabled.
This step is required when using sipXcom release 14.10 and higher with the BLA feature enabled. The issue has been pinpointed to default SIP server IP address not being passed to the phones. The workaround is to statically provision the IP Address in the Phones->Mac-address->SIP Servers menu, and resending the profiles for each phone. The preferred method is to create a phone group, make the change in the Polycom SIP Servers section, and then assign each phone with BLA capability to the phone group.
Enabling BLA in sipXcom release 14.10 and above only works today in single-server sipXcom installations. Enabling BLA in this manner may cause issues when building high-availability sipXcom systems. There is work underway by eZuce developers to understand why BLA does not work when the outbound SIP proxy server is not explicitly provisioned.
When using BLA on the main line, a suggested best practice is to place the main in a hunt group - this provides the greatest flexibility for implementing three options.