Call control procedures 5-9
Digital Switching Systems DMS-250 ISDN Reference Manual MWC14 (CSP14)
the BCHNEG setting in table TRKSGRP. This parameter establishes
B-channel negotiation.
If B-channel negotiation is disabled, the switch drops the connection if the
B-channel requested in the SETUP message is not available.
Datafill for enabled B-channel
Enabled B-channel negotiation occurs if the BCHNEG parameter is set to Y
(yes). To complete the connection, the switch selects any other B-channel
associated with the D-channel. This is the preferred setting for the BCHNEG
parameter.
If B-channel negotiation is enabled (BCHNEG = Y), the following settings
apply:
• Set BCHGLARE parameter in table TRKSGRP to STAND.
No other value is allowed for this parameter when BCHNEG = Y. If an
attempt is made to datafill the value of YIELD, the input value is ignored
and STAND is substituted.
• Set the following office parameters in the table OFCENG (values shown
are recommended):
NO_OF_FTR_CONTROL_BLKS = 125
NO_OF_SMALL_FTR_DATA_BLKS = 1 (not used, but must not be 0)
NO_OF_MEDIUM_FTR_DATA_BLKS = 125
NO_OF_LARGE_FTR_DATA_BLKS = 1 (not used, but must not be 0)
Datafill for disabled B-channel
Disabled B-channel negotiation occurs if the BCHNEG parameter is set to N
(no).
Call proceeding and termination
After successful translation of the called party number, the network chooses
an outgoing route and proceeds to terminate the call. When the outgoing
channel (PRI or non-ISDN) is successfully allocated, a CALL PROC
message is sent over the originating PRI interface. This message contains the
originating channel identification allocated by the network. Next, the voice
path between the originating and terminating interfaces is established so that
ringing is passed in-band by the terminating office.
In the event that an outgoing route cannot be successfully allocated, a CALL
PROC message may be sent to the originating PRI interface as described in
“Call routed to treatment” in this chapter.
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