Cisco Cisco IOS Software Release 12.4(2)XB6

When an outgoing voice call is preempted by a DDR backup call, the preemption call treatment starts 
by providing a preemption tone and starting the tone timer.

An MLPP preemption tone is a special tone played to the voice call announcing that the line is about to 
be seized by a call with a higher precedence. A steady tone, 1060 ms in duration, is played on all legs of 
the call until the user hangs up or the preemption tone times out.

For the telephony leg of the call, the preemption tone is played using the DSP.

For the IP leg (across the VoIP network) of the call, the preemption tone is played as media.

For the ephone leg on Cisco CME, a reorder tone is played for the local user and a preemption tone 
is played for the remote user. 

When the preemption tone timer is expired and the call is still in a connected state, both call legs are 
disconnected by the gateway with the following cause code:

If you release the call before the preemption tone timer expires, the following cause code is used:

In both cases, the following internal cause code is used for the release calls:

This section describes the tasks required to configure integrated services for ISDN interfaces:

 (Required)

 (Optional)

An ISDN serial interface configured for integrated mode supports data and voice calls using incoming 
call type checking to accept incoming voice and data calls when an inbound voice dial peer is matched.

Perform the following tasks to configure integrated services: