Nortel DMS-100 Series Maintenance Manual page 128

2-52 Functional overview
When a drawer state changes to ISTb or SysB, the state of the OPM changes
to ISTb or SysB.
Detection of some drawer ISTb conditions can occur only when the drawer or
the PM is OOS. These conditions include BIC scan, BIC inhibit, BIC CM and
BIC activity. Drawers with these conditions can be returned to service with an
ISTb condition. When this event occurs, the ISTb state clears when the InSv
unit or drawer tests occur. The sequence of events follow:
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The list of full InSv tests follows:
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297-8361-550 Standard 04.02 December 2004
The BIC looparound sets the drawer to the SysB state. This condition does
not allow the BIC looparound to send messages to the BIC looparound. All
lines to the drawer are made line maintenance busy (LMB) because the call
processing is disabled.
The BIC scan sends a scan message to the BIC. This message makes sure
the scan chip can detect supervision changes on all datafilled lines. The
path through the DCC is similar to the BIC looparound because this action
involves a message.
The DCC looparound tests a loop in the DCC. The looparound does not
test all the DCC hardware for the DCC/BIC communication. When a fault
occurs with this hardware, the DCC looparound passes when following
BIC looparound tests fail. An accurate drawer fault does not occur.
The DCC/BIC looparound sets the drawer to the ISTb state. A failure on
the speech path hardware to the drawer occurs. When a specific channel
fails the test, all channels are not always affected. Call processing is
possible at this time. For this reason, the drawer state is updated to ISTb
at the MAP display and the drawer can handle call processing. The
DCC/BIC looparound sends test patterns to the BIC to test the PCM path.
The patterns that the transmit time switch receives are expected to be the
same in a timeout period.
ACTIVITY_READ
MSG_LOOPAROUND
ANI_COIN_FAIL
PARITY_TRAP_FAIL
BIC_ACT_TEST
POWER_CONVERTER_FAIL
BIC_CM_TEST
RINGING_FAIL
BIC_INHIBIT_TEST
RTM_CM_TEST