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6 backward alarms – Comtech EF Data SDM-9000 User Manual

Page 184

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Maintenance

SDM-9000 Satellite Modem

6–26

Rev. 4

6.2.2.2.6 Backward Alarms

Fault/Alarm

Possible Problem and Action

BW ALARM RX4

Receive backward alarm #4.

The distant end of the link is sending Backward Alarm #4. This
indicates trouble at the distant end, which may be a result of improper
transmission at the near end of the link. The modem will signal this
event by setting the deferred maintenance alarm (open collector). This
is essentially a monitor function so the modem reports and records the
event, but takes no other action. Refer to Chapter 2 for the backward
alarm theory of operation. If the user does not wish to monitor the
backward alarm faults, the backward alarm inputs must be grounded at
the breakout panel. Refer to the B141-1 Breakout Panel Installation
and Operation Manual
for breakout panel pinouts.

BW ALARM RX3

Receive backward alarm #3.

Refer to BW alarm RX 4 for details.

BW ALARM RX2

Receive backward alarm #2.

Refer to BW alarm RX 4 for details.

BW ALARM RX1

Receive backward alarm #1.

Refer to BW alarm RX 4 for details.

BW ALARM TX4

Transmit backward alarm #4.

The modem is being instructed to send backward alarm #4 to the
distant end of the link. This is controlled by wiring the backward alarm
inputs of the modem to the Demod fault relay and/or other fault outputs
in the receive system (see IESS-308 for clarification). The simplest
implementation for single destination service is to wire the Demod fault
relay between ground and the four backward alarm inputs (see
Chapter 2 for clarification). This sends all four backward alarms in the
event of any major (prompt) receive fault. This particular alarm is
transmitted, reported, and recorded, but the modem takes no other
action. In most cases, this will be sent due to some receive problem
with the modem, so a real fault will probably be occurring if backward
alarms are being sent. The transmit backward alarms are a symptom
of trouble, not a cause.

BW ALARM TX3

Transmit backward alarm #3.

Refer to BW alarm TX 4 for details.

BW ALARM TX2

Transmit backward alarm #2.

Refer to BW alarm TX 4 for details.

BW ALARM TX1

Transmit backward alarm #1.

Refer to BW alarm TX 4 for details.