Nortel DMS-100 Series Maintenance Manual page 117

The primary functions of the NTRX42 are as follows:
to monitor and detect converter failures
to trip breakers when overcurrent conditions exist
to trip breakers on converter failure
to provide battery feed samples for the alarm module
to respond to ARLB conditions
The NTRX42 contains the following operating blocks:
ARLB
trip circuitry and enable
breakers
Trip and enable circuitry A transistor circuit trips the associated circuit
breaker in response to alarm relay release in the associated power converter
or RG. This circuitry provides the DRIVE or ENABLE signal for the
converters that require these signals.
Breakers Two magnetic breakers stack one on top of the other in this
breaker module. The breakers operate over the whole –48 V to –60 V range.
Fan alarm module (NTRX66AA)
The fan alarm module monitors the fans in the roof and the auxiliary cooling
units. The fan alarm module determines when any fans do not operate.
The module monitors round, 6-inch, tube-axial fans. The fans are arranged
in two banks. The intake fans are arranged in cooling units below the
components in the electronics compartment. The exhaust fans are in the
roof.
When the temperature inside the cabinet rises above 65F (18 C), the bank of
exhaust fans activate. The bay operates continuously.
The fan alarm module monitors the operation of the fans. The alarm can
notify the NTRX41AA alarm module when the temperature inside the
cabinet rises. The alarm notifies the NTRX41AA when the temperature
level must start the exhaust fans and the fans do not operate. When at any
time the fans do not operate, the fan alarm module signals the NTRX41AA
alarm module.
When a fan fails, the fan alarm module signals to the alarm module turns on
the fan fail and frame fail lights. The fan fail lights and frame fail lights are
on the MSP cover. The fan alarm module notifies the system of
environmental control failure through the NT0X10 scan card in the RMM.
DMS-100 Family OPAC Maintenance Manual XPM12 and up
OPAC maintenance overview 2-23