Chapter 4. Troubleshooting and Diagnostics ASM-20 Installation and Operation Manual
4-2 Bit Error Rate Tester (BERT) 11/4/99 12:34
Table 4-1 Differences in Versions (Cont.)
ASM-20 ASM-20-2
Metal box Plastic box
Terminal block with screws Clip terminal block
Main chip RJ008 and external
BERT chip
Main chip RJ016 which includes
BERT chip
No CE mark CE mark
No asynchronous transmission Asynchronous transmission
capability
The above versions are compatible with each other within similar
synchronous rates.
Additionally, the ASM-20-2 has been improved in order to get a better line
surge protection. In many cases line surges are caused by lightening strikes.
The improved line protection of ASM-20-2 complies with the ITU-T/K.21
standard.
The line interface has been modified by adding two Gas surge protection
diodes and another two Transorber surge protection diodes. The Gas diodes
protect against line surges above 300V and the Transorber diodes protect
against surges below 300V.
4.3 Loop Tests Procedure
The test switches and LED indicators built into ASM-20 allow rapid checking
of the data terminals, ASM-20 and lines. Use the test procedures provided in
this chapter to check normal system operation and isolate faulty equipment
in the event of failure. Each test verifies the operational performance of a
unit in the system or provides a positive indication of equipment failure.
Before testing operation of the data system equipment and line circuits,
ensure that all units are turned on and correctly configured.
4.4 Bit Error Rate Tester (BERT)
The Bit Error Rate Tester (BERT) can be activated in any diagnostics test in
which the test pattern transmitted is looped back to the BERT for
comparison (see Figure 4-1).