Test Modes; Interface Loopback; Figure A-17. Co-Located Modulator And Demodulator; A.6.7 Test Modes - Comtech EF Data SDM-2020 Installation And Operation Manual

SDM-2020 Satellite Demodulator
A.6.7

Test Modes

A.6.7.1

Interface Loopback

The unit provides an "Interface-Loopback" test mode of operation. When loopback mode
is executed (turned on), send data (SD) at the input to the interface is routed to both the
interface receive data (RD) output and the host modulator data input.
Send data (SD) is routed through as much of the interface circuitry as possible before
being returned to the receive data (RD) output. This mode of operation does not disrupt
transmission of data over the satellite link when installed in an SDM-2020 modulator.
Rev.3
SD
RD
SD
Demodulator
RD

Figure A-17. Co-Located Modulator and Demodulator

Tx IF
Modulator
Rx IF
Data Interfaces
A–53