Comtech EF Data SDM-300A - Manual (Page 121)

SDM-300A Satellite Modem Revision 6
Front Panel Operation MN/SDM300A.IOM
5–27
FUNCTION SELECT: CONFIGURATION: INTERFACE:
B-BAND LOOP BACK
B-BAND LOOP BACK
OFF
IMPORTANT
This is a Test Mode.
Baseband Loopback Operation: On or Off
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 5-6 for a block diagram of baseband loopback operation.
CUSTOMER
DATA
IBS OR IDR
INTERFACE
ENCODER/
MODULATOR
TRANSMIT RF
EQUIPMENT
ANTENNA
AC POWER POWER SUPPLY
MICRO-
COMPUTER
REMOTE SERIAL
INTERFACE
FAULT INDICATORS
RECEIVE RF
EQUIPMENT
DEMODULATOR/
DECODER
SATELLITE MODEM
Figure 5-6. Baseband Loopback
Note: When baseband loopback is turned on, data is looped back on the customer side of the interface. This is a bi-directional loopback of
the baseband data. This test mode will verify the customer equipment and cabling between the modem and the customer equipment. The
baseband loopback is not bi-directional in D&I.