Specifications

Chapter 4 Diagnostics ASM-10/8 Installation and Operation Manual
4-2 V.54 Loopback Tests
Local Analog Loopback (LLB)
The local analog loopback (LLB) test checks the performance of the local
ASM-10/8 modem, the local DTE, and the connections between them (see
Figure 4-1). The test is performed separately at the local and the remote site.
ASM-10/8
Line
Interface
DTE
Transmit
Receive
Data
Clock
Clock
Data
ANA
Depressed
Figure 4-1. Local Analog Loopback

To perform the local analog loopback test:
1. Press the ANA pushbutton.
The TEST LED on the ASM-10/8 front panel lights up. The modem's
transmit output is now connected to its own receiver.
2. Execute the local analog loopback with one of the following methods:
 Using the DTE configured to the half duplex operation and checking the
echoed data stream.
 Using an external BER tester.
If the BER test indicates an error-free data stream, but the DTE test indicates
a fault, verify that the cable between the DTE and ASM-10/8 is properly
connected. If the problem persists, follow the DTE manufacturer's test
procedures.
3. To isolate a communication line problem, perform the LLB loopback at the
opposite end. If both LLB tests are error-free, the fault is probably in the
communication line or in the line interfaces.
4. After completing the test or correcting the fault, press ANA pushbutton again
to restore it to the Off position.