363-206-305
Power
4-12
Issue 3 June 2000
AUA421 Channel and Drop Test Unit (CDTU)
4
The CDTU circuit pack is used in the
SLC
-
2000 MSDT as well as the DDM-2000
FiberReach narrowband shelf. This circuit pack provides the remote end
terminations and detectors required to support end-to-end channel testing of two-
wire locally-switched services, such as POTS, coin, and multiparty services.
When a channel test request is received on the narrowband shelf, the DSXBIU
instructs the channel unit associated with the channel under test to operate its test
relay. The DSXBIU then informs the CDTU that a test is occurring, and the CDTU
then performs a drop test and reports the results back to the DSXBIU. The CDTU
provides channel test terminations in sequence based on results from the channel
test detectors and instructions from the DSXBIU. This circuit pack is optional.
LEDs
4
Two green power on (PWR ON) indicators on the user panel show that the shelf is
receiving fused
−
48 volt power from each of two services. The indicator remains
illuminated as long as the associated
−
48 volt feeder is supplying power to the
shelf.
Normally the FAULT LED on the circuit pack faceplates is operated via the
controller which provides a ground return for current generated by the on-board
converter. In the event of a DC-to-DC converter failure, the LED will be operated
via the
−
48 volt power leads. The
−
48 volt power leads are supplied through an
electronic gate or relay contact normally held open by the converter. The power,
fusing, and LED circuits shown in Figure 4-9, are used on all circuit packs with on-
board DC-to-DC converters.
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