Drawer Testing - Nortel DMS-100 Series Maintenance Manual

Drawer testing

To ensure that message and speech data can be sent to and from the BIC, the
RLCM-EDC conducts a BIC looparound test to detect line drawer faults. If
the BIC test fails, the CC implements a full in-service test on both BICs, to
ensure the fault is not transient or from the DCC or processor card.
If any of the BIC or DCC tests fail, the LCM is not forced into takeover
mode.
If a drawer state changes to ISTb or SysB, the state of the RLCM-EDC also
changes to ISTb or SysB.
Some drawer ISTb conditions can be detected only 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 returned to service with an
ISTb condition, the ISTb state is cleared when the InSv unit or drawer tests
are performed.
BIC looparound sets the drawer to the SysB state so it cannot have
messages sent to it. All lines to the drawer are made line maintenance
busy (LMB), since the call processing is disabled.
BIC scan sends a scan message to the BIC to ensure the scan chip can
detect supervision changes on all datafilled lines. Since this involves a
message, the path through the DCC is similar to the BIC looparound.
DCC looparound tests a loop in the DCC. The looparound does not test
all the DCC hardware for the DCC/BIC communication. If a fault exists
with this hardware, the DCC looparound passes while subsequent BIC
looparound tests fail, even though no drawer fault actually exists.
DCC/BIC looparound sets the drawer to the ISTb state. A failure on the
speech path hardware to the drawer has occurred. Although a particular
channel may have failed the test, it is not certain if all channels are
affected. Call processing may still be possible. For this reason, the
drawer state is updated to ISTb at the MAP display, but the drawer is not
prevented from handling call processing. The DCC/BIC looparound
tests the PCM path by sending test patterns to the BIC. The patterns
received by the transmit time switch are expected to be the same within a
timeout period.
The list of full InSv tests follows:
lcc_la_test_code
bic_msg_test_all
is_dcc_commssng_la_test
rd_td_test_all
Maintenance overview 1-61
DMS-100 Family Maintenance Manual ABSK007