AM64/128A User Manual | Test Menu |
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5.4.6 In Service Test
5.4.6.1 Overview
This mode allows the error performance of the line to be monitored, without interrupting data traffic. This works by monitoring the accuracy of some of the overhead bits that make up the transmission frame structure. As the data channel itself is not monitored, the figures produced cannot accurately be extrapolated to give the data error rate, but can be used as a general guide. In order to understand this feature better, an understanding of the transmission frame structure is required. This is included as Appendix C. A brief discussion on the operation is as follows.
5.4.6.2 Operation
The display to select in the test menu is
T > In Svc Test
The mode can be exited and
(1)Comms framing error display
(2)Received envelope errors
(3)Transmitted envelope errors (master only)
(4)Time of test
The SELECT and SCROLL keys operate in the same manner as in Data Test.
This mode may be left running over a long period, so an abort indication has been added to the displays. The character ‘a’ is displayed prior to the count if the test has been aborted. The monitoring is aborted when the system error rates get so high that the envelope alignment pattern / comms framing word can not be locked on to, or when the system loses line sync. (The error count would be meaningless if the line had been broken in the middle of a test). Note that the different displays may abort at different times, but the clock will stop when the first abort occurs.
The error count displays appear as follows: (refer to Appendix C for greater detail)
Comms 000000
Evp Rx 000000
Evp Tx 000000
Comms word error count.
Received envelope errors.
Transmitted envelope errors (Master mode only).
The time display simply shows the time since the test has started in seconds.
For example
Time 000010 | If the count is stopped the display is | T Stop 000010 |
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If the count has been aborted the display is
T Abort 000010
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