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104
LEDR Series I/O Guide
MDS 05-3627A01, Rev. D
The front panel of the Protected Switch Chassis (PSC) has only two
LEDs and an RJ-11 jack for an orderwire handset. The LEDs indicate
by light and an arrow outline which LEDR chassis is active. It is
assumed the two LEDR chassis will be mounted above and below the
PSC with Unit A on top and Unit B on the bottom.
11.2 Protected Operation
During normal operation, one radio path is selected and the RF and
interface switches are set to service that path. (The illuminated
POWER
LED indicator on the front panel of the Protected Switch Chassis (PSC)
points to the currently active unit.) A switch in the transmitter circuitry
allows one transmitter to be connected to the common
ANTENNA
port on
the Protected Switch Chassis. On the receive path, a splitter in the Pro-
tected Switch Chassis allows both radio receivers to receive the
incoming RF signal for processing.
The Protected Switch Chassis is a gateway for data coming and going
between each of the LEDR radio units and the common data circuits
connected to the PSC. The PSC monitors various RF and data signal
paths for predefined fault-determining parameters. If signal conditions
are not normal, the PSC’s microprocessor controller will issue an alarm
and move the standby LEDR radio to the active mode.
Fault-determining parameters can be programmed from the Network
Management System (NMS) software. Examples of these parameters
are:
• Low RF output power
• High transmitter temperature
• Synthesizer out-of-lock
• Problem with the option board or framers
• CPU failure wherein the CPU watchdog causes a reset
Transmitter Failure
Any failure on the “active” transmitter path will create a fault condition
which will place the currently active transmitter on standby and switch
the “standby” transmitter to “active.” The newly active transmit path
will remain in use until a manual changeover returns the configuration
to the original transmitter path. This allows the link to remain fully oper-
ational until the user has replaced the faulty transmitter circuitry.