Comtech EF Data SDM-309B - Manual (Page 161)

Maintenance SDM-309B Satellite Modem
6-6–16 MN/U-SDM309B Rev. #
6.3.1 Transmit Overhead Framing Unit Faults
Fault Possible Problem And Action
DATA/AIS Data or Incoming Alarm Indication Signal.
When AIS (Alarm Indication Signal) is selected the TX_INTF
(Transmit Interface) fault “Data/AIS is monitoring a fault condition
of all 1’s from customer data input to the modem. When Data_Flt
is selected, the TX_INTF fault “Data/AIS is monitoring a fault
condition of all 1’s or all 0’s. This is referred to as a data stable
condition which means the 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, to help
isolate the source of the trouble in a system.
TX_PLL (IBS/M1200P Only) Indicates a loss of lock on the reference of the
interface transmit clock recovery oscillator. Return the interface
card for repair.
DROP (D&I/M1200P Only) Drop Interface Hardware Fault.
The typical cause of this fault is the drop phase locked loop is not
locked or some other drop interface hard- ware has malfunctioned.
Return the drop and insert channel unit to the factory for repair.
Clk_Act Loss of activity on the selected transmit clock source. The modem
will fallback to the internal SCT clock source with an accuracy of
10-5.
6.3.2 Receive Overhead Framing Unit Faults
Fault Possible Problem And Action
BUF_UNFL Buffer Underflow, the plesiochronous buffer has underflowed. As buffer
underflow is normally a momentary fault (there are clock problems if this is
continuously present) this is included in this Section to be consistent with
the fault reporting system and be correctly registered in the ‘stored Fault"
memory. The time and date of the last 10 Receive "OFU" faults are stored
in battery backed memory as an aid to trouble shooting. The interval
between stored Over-flow/Underflow events can be used to determine
relative clock accuracies.
BUF_OVFL Buffer Overflow, the plesiochronous buffer has overflowed. See the
"BUF_UNFL" Section for problems and actions as the same comments
apply.
Data/AIS Data or incoming Alarm Indication Signal.
The data monitored for Receive Data is coming from the Satellite. When
AIS (Alarm Indication Signal) is selected the RX_INTF (Receive Interface)
fault “Data/AIS is monitoring a fault condition of all 1’s from customer the
satellite. When Data_Flt is selected, the RX_INTF fault “Data/AIS is
monitoring a fault condition of all 1’s or all 0’s. This is referred to as a data
stable condition which means the data is not transitioning.
This indicates there is trouble in receiving data from the satellite. The
modem passes this signal transparently and takes no other action. This
indication is a monitor function only, to help isolate the source of trouble in
a system.