ASM-20 Installation and Operation Manual Chapter 4. Troubleshooting and Diagnostics
11/4/99 12:34 Communication Link Tests 4-5
To check the performance of the local modem and the local data terminal:
1. Press the ANA (Analog Loopback) push button on the front panel (see
Figure 3-1). This test can also be activated via the pin on the DTE
interface. See Table 2-2 for more information. The TEST LED should
turn on. ASM-20 transmit output is now connected to its own receiver
(see Figure 4-3).
2. Check that the DTE is operating properly and can be used for a test. If a
fault is indicated, call a technician or replace the unit.
3. Execute the test using one of the methods described below:
• Use the DTE and check the echoed data stream
• Use an external Bit Error Rate Tester (BERT) unit
• Use the internal Bit Error Rate Tester (BERT). Press the PATT push
button. The ERR LED will light up briefly to indicate that the LED is
functioning. If any bit error is encountered, the LED will blink or
remain ON.
4. Perform Step 3 at both ends. If the BERT test equipment does not
indicate a fault, but the data terminal does, follow the manufacturer’s
test procedures for the data terminal and check that the cable
connecting the terminal and ASM-20 is working. After completion of the
test (or when the fault has been corrected), restore the ANA push
button to the OFF position by pressing the ANA push button again.
Proceed to Communication Link Tests below.

4.7 Communication Link Tests

Remote Digital

Loopback

This test determines the performance of the local and remote ASM-20, and
the lines connecting them.
To check the performance of the local and remote ASM-20:
1. Press the REM (Remote Loopback) push button, providing a loopback at
the remote ASM-20 (see Figure 4-4). (This test can also be activated via
the pin on the DTE interface.) The TEST LED should light up at both the
local and remote units.
2. Perform the BERT test using one of the methods described below:
• Use the DTE and check the echoed data stream
• Use an external Bit Error Rate Tester (BERT) unit
• Use the internal Bit Error Rate Tester (BERT). Press the PATT push
button. The ERR LED will light up briefly to indicate that the LED is
functioning. If any bit error is encountered the LED will blink or
remain ON.