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SDM-300A Satellite Modem
5.2.3.3
Transmit Interface Faults
Fault/Alarm
TX DROP
TX DATA/AIS
TX CLOCK PLL
TX CLOCK ACT
Rev. 4
Possible Problem and Action
Drop interface hardware fault (D&I only).
The typical cause of this fault is the drop phase-locked loop is not
locked, or some other drop interface hardware has malfunctioned.
Contact the Comtech EFData Customer Support Department.
Data or incoming AIS.
When the AIS is selected in the Interface Utility menu for TX data
fault, the transmit interface fault TX data/AIS is monitoring a fault
condition of all 1s from customer data input to the modem. When data
is selected in the Interface Utility menu for TX data fault, the TX
interface fault TX data/AIS is monitoring a fault condition of all 1s or
0s. This is referred to as a data-stable condition (data is not
transitioning). This fault indicates there is trouble in the chain sending
data to the modem. The modem passes this signal transparently, and
takes no other action. This indication is a monitor function only, and
aids in isolating the trouble source in a system.
Transmitter phase-locked loop fault.
Indicates the transmitter PLL is not locked to the reference of the
interface transmit clock recovery oscillator. Contact the Comtech
EFData Customer Support Department.
Activity detector alarm of the selected interface transmit clock.
Indicates the selected TX clock is not being detected. Check the signal
of the selected TX clock source to verify the signal is present. The
interface will fall back to the internal clock when this alarm is active.
Maintenance
5–15
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