A branch conference site accesses the optical transmission by HDSL, it works normally until one time that the picture isn’t clear and the sound is very noisy.
The front 2 bits of the chip state is unstable, multi-frame synchronism unstable, CRC is around 80%.
Help the client in phone to do the loop test, focus the fault on the HDSL. But the client considers it as normal that the HDSL indicator lamp didn’t change, the high class test from the transmission room to the conference site is normal. Manipulate the circuitry test button, the alarm as old.
HSDL support the 64K bit rate very well, but can’t bearer the 1920K bits rate very well. The next day restart the equipment, the HSDL can support the 1920K bit rate well, so the problem may be caused by the initialization.