2 B L Oopback Features (Terrestrial & If) - Comtech EF Data DMD50 Installation And Operation Manual

DMD50 Universal Satellite Modem
3.6 Loopback Features (Terrestrial & IF)
The modem provides for a number of different loopbacks. The Loopback supported are:

IF Loopback – Tx IF port is looped back to the Rx IF port
 TX Terrestrial Loopback - Tx Data port is looped back to the Rx Data port after the
interface driver/receiver. (prior to the framing unit)

TX Baseband Loopback - Tx Data port is looped back to the Rx Data port after the
interface driver/receiver. (after the fraiming unit)

RX Terrestrail Loopback - Receive Data from the satellite is looped back for retransmission
to the satellite, providing a far end loopback. (prior to the framing

RX Baseband Loopback - Receive Data from the satellite is looped back for retransmission
to the satellite, providing a far end loopback. (after to framing unit)

TX/RX Terrestrial Loopback - provides both Terrestrail loopbacks simultaneously

TX/RX Baseband Loopback - provides both Baseband loopbacks simultaneously
Usage of the modems loopback capabilities in conjunction with the Ethernet
data interface can produce undersirable network loops. In order to run any
type of data test with an Ethernet interface you must utilize two modems
connected back to back. Simply using one modem and a loopback will not
MN-DMD50– Revision 3
produce the desired results.
Theory of Operation
unit)
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