Nortel DMS-100 Series Maintenance Manual page 81

in-service test to make sure the fault is not transient or from the DCC or
processor card.
If one of the BIC or DCC tests fail, the LCM is not forced to takeover mode.
If a drawer state changes to ISTb or SysB, the state of the RLCM also
changes to ISTb or SysB.
The system can detect some drawer ISTb conditions when the drawer or the
PM is OOS. These conditions include BIC scan, BIC inhibit, BIC CM, and
BIC activity. If drawers with these conditions are RTS with an ISTb
condition, the system clears the ISTb state when the InSv unit or drawer
tests occur. The sequence of events is as follows:
The BIC looparound sets the drawer to the SysB state so the drawer
cannot receive messages. The lines to the drawer are set to line
maintenance busy (LMB) because the call processing is disabled.
The BIC scan sends a scan message to the BIC to make sure the scan
chip can detect supervision changes on each line that holds data. The
path through the DCC is like the BIC looparound because this step
involves a message.
The DCC looparound tests a loop in the DCC. The looparound does not
test the DCC hardware for the DCC/BIC communication. If a fault is
present with this hardware, the DCC looparound passes while the next
BIC looparound tests fail, even though a drawer fault is not present.
The DCC/BIC looparound sets the drawer to the ISTb state. A failure on
the speech path hardware to the drawer occurs. A channel can fail the
test. Call processing can occur. The drawer state updates to ISTb at the
MAP display and continues to 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 must be the same in a
timeout period.
The list of full INSV tests follows:
ACTIVITY_READ
MSG_LOOPAROUND
ANI_COIN_FAIL
PARITY_TRAP_FAIL
BIC_ACT_TEST
POWER_CONVERTER_FAIL
BIC_CM_TEST
DMS-100 Family RLCM Maintenance Manual XPM12 and up
Maintenance overview 1-65