Page 78 of 910 Features
553-3001-365 Standard 4.00 August 2005

Minimum requirements

The ACF feature for IP Phones has the following minimum requirements:
• Call Server must be running CS 1000 Release 4.5 software.
• LTPS must be running IP Line 4.5 software.
• IP Phones (including IP Softphone 2050) must support Unistim version
2.9. (Use the isetShow command to determine the Unistim version. One
of the columns in the isetShow output is UNIStimVsn.)

ACF mode

The ACF feature for IP Phones enables an IP Phone to reregister in the ACF
mode during a supported system failure.
The ACF mode preserves the following:
• active media session
• LED states of the Mute, Handsfree, and Headset keys
• DRAM content
Note: All other elements (the feature keys, soft keys and text areas) are
retained until the user presses a key or the connection with the Call
Server is resumed. If the user presses a key during the failover, the
display is cleared and a localized “Server Unreachable” message is
displayed.
The IP Phone uses this new mode of re-registration only when the Call Server
explicitly tells the IP Phone to do so. IP Phones clear all call information if
they register to a Call Server or LTPS that does not support the ACF feature.
IP Phone ACF timer
It is possible that there may be an LTPS supporting the ACF feature and an
LTPS that does not support the feature in the same system.
A situation could exist where it takes a long time to fix a failure and no
failover Call Server is available. During this time, the user may have released
the call by pressing the Release key or hanging up the telephone. In this case,