Comtech EF Data SDM-300L3 - Manual (Page 98)

SDM-300L3 Satellite Modem Revision 1
Front Panel Operation MN/SDM300L3.IOM
4–30
FUNCTION SELECT: CONFIGURATION: INTERFACE:
B-BAND LOOP BACK
B-BAND LOOP BACK
OFF
IMPORTANT
This is a Test Mode.
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
4-6 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 4-6. 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.