Comtech EF Data SDM-300A, Installation And Operation Manual

Page: 73 / 398

Operation SDM-300A Satellite Modem
3–20 Rev. 4
B-BAND LOOP BACK
(Test Mode Configuration)
Programs the modem for baseband loopback operation.
When baseband loopback is turned on, the data and timing signals are
switched from the demodulator to the modulator on the modem side of
the interface. The DTE baseband signals are also looped back from the
transmitter data and clock to receiver data and clock on the customer
side of the interface. This is a bi-directional loopback of the baseband
data. Refer to Figure 3-25 for a block diagram of baseband loopback
operation.
Upon entry, the status is displayed. Press [
↑
] or [
↓
] to make the
selection. Press [ENTER] to execute the change.
INTERFACE LOOPBACK
(Test Mode Configuration)
Programs the modem for Interface Loopback operation.
When INTERFACE LOOPBACK is turned on, data is looped back at
the modem side of the interface. This is a bi-directional loop back of
the data after the base band data has had the overhead added. Refer to
Figure 3-26 for the interface loopback block diagram.
Upon entry, the status is displayed. [
↑
] or [
↓
] to make the selection.
Press [ENTER] to execute the change.
Note: This menu is only available when the overhead interface PCB or
Reed-Solomon PCB is installed.
LOOP TIMING The SCT output will become phase-locked to the RX satellite clock.
TX and RX data rates must be equal unless the asymmetrical loop
timing option is enabled.
Upon entry, the status is displayed. Press [
↑
] or [
↓
] to make the
selection. Press [ENTER] to execute the change.
TX DATA FAULT
Transmit data fault. Press [
↑
] or [
↓
] to select one of the following
modes:
•
NONE: The transmit interface fault Data/AIS is not activated.
•
Alarm Indication Signal (AIS): Sets transmit interface fault
Data/AIS to monitor a fault condition of all 1s from customer
data input to the modem.
•
DATA: Sets transmit interface fault Data/AIS to monitor a
fault condition of all 1s or 0s. This is referred to as a data-
stable condition, which means that the data is not
transitioning.
Upon entry, the current TX data fault that is being monitored is
displayed. Press [
↑
] or [
↓
] to make the selection. Press [ENTER] to
execute the change.
Note: This menu is only available when the overhead interface PCB is
installed.