DS-1 configuration 2-11
Digital Switching Systems DMS-250 ISDN Reference Manual MWC14 (CSP14)
When a remote alarm is detected in the receive path, the alarm is verified
through a filtering process. The filtering process meets requirements as
defined by Bell Publications 43801 (United States) and CS03 (Canada).
The filtering process operates as follows:
• When the remote alarm mode is entered, a counter integrates the
detected remote alarm from the digital carrier in increments of 10 ms.
• For each time period with a detected remote alarm, the counter
increments by one. When a detected remote alarm is no longer present,
the counter decrements by 16.
• A remote alarm is considered significant when the counter reaches 34
(340 ms of continuous remote alarm). When the alarm is significant, the
counter no longer increments.
• When the remote alarm mode is exited, the counter decrements until it
reaches zero (this takes approximately 30 ms when the remote alarm is
absent).
• If any frame alarm is present, processing of the yellow alarm is
temporarily suspended and the contents of the yellow alarm counter
remain unchanged.
LCGA—red alarm
The local carrier group alarm indicates a local alarm in the transmit path. If
the switch determines that a DS-1 trunk should be removed from service it
generates a local alarm. As part of this operation, the DS-1 trunk transmits a
remote alarm pattern to inform the far end of its local alarm condition.
When the DS-1 trunk sends a remote alarm, it sends alarm patterns as
follows:
• When the DS-1 trunk is commanded to enter the local alarm mode, a
remote alarm pattern is transmitted. This pattern transmission is delayed
for 2.5 ± 0.5 s after the receipt of the message from a DMS-250 switch.
• When the DS-1 trunk is commanded to exit the local alarm mode, it
stops sending the remote alarm pattern. There is a 10.5
± 0.5 s delay after
the receipt of the message from the DMS-250 switch. The DS-1 trunk
informs the DMS-250 switch when the remote alarm pattern ends.
Display fields
The display fields applicable to DS-1 trunks are as follows:
• frame slip
• frame loss
• approximated BER
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