ADTRAN DSU 56 user manual Loop only Test RT, Loop Only Test Diagram

Chapter 3. Test Modes

LOOP ONLY TEST (RT)

The LOOP ONLY test or REMOTE LOOPBACK test (RT) is used to test the loop interface and a major portion of the DTE interface of the local DSU 56/64 from the remote site over the actual digital data circuit.

For the LOOP ONLY test, the network receive data is looped to the network transmit data inside the DTE interface section of the DSU 56/64. The physical DTE interface is ignored for this test. The LOOP LED flashes during initialization of the test and turns on solid once the test is in progress. Figure 3-4 illustrates the loopback point and the signal paths for this test.

DTE or Test Equipment Interface

TD

RD

	56/64 DSU
DTE	Loop
Transmit	Transmit
Interface	Interface
	Loop
	Only
DTE	Loop
Receive	Receive
Interface	Interface

Network Interface

Loop TX

Loop RX

Figure 3-4. Loop Only Test Diagram

To initiate the LOOP ONLY test, perform the following steps:

1.Press SELECT four times to turn on the LOOP test indicator.

2.Press TEST while this test indicator is on.

3.To terminate this test, press TEST.

3-6 DSU 56/64 User Manual 61200062L1-1