User`s guide

Dialogic
®
System Release 6.0 PCI for Windows
®
Release Update, Rev 62 — January 30, 2008 223
Dialogic Corporation
For further information about CDP files, see the Dialogic
®
Global Call Country Dependent
Parameters (CDP) for PDK Protocols Configuration Guide.
1.56 New Channel Block Timer for NTT Protocol
A new channel block timer parameter has been added to the ntt.prm file for the ISDN NTT
protocol. The purpose of this timer is to block the first response (i.e., PROCEEDING,
ALERTING, or CONNECT) to an incoming call (i.e., SETUP message) on a channel, if
that same channel has just recently had a previous call released. The channel is blocked
for the amount of time specified by this new channel block timer parameter.
This feature is supported on Dialogic
®
D/240JCT-T1, D/480JCT-1T1, and D/480JCT-2T1
Media Boards:
1.56.1 Feature Description
On some NTT switches, if a call initiated from the switch is responded to with a
PROCEEDING message too quickly (i.e., response to the SETUP message) on a recently
released channel, the switch rejects the call with ISDN cause 44 (requested
circuit/channel not available) and sends an error message (voice message) to the
subscriber. This also applies to other first response messages like ALERTING and
CONNECT.
For example, the following figure gives an example of a problematical sequence where
ISDN cause 44 is returned when channel 12 is reassigned in 31 milliseconds.