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Different external-calling number configurations have different result when use VP8620 in private ISDN networking

Publication Date:  2019-07-23 Views:  131 Downloads:  0

Issue Description

There is only one MCU ( vision 2.21), and there are 21 terminals( vision 2.90). MCU connect switch by 5 PRI.
When playing 4 channel conference implement, some terminal and MCU will have large CRC verification bit error (80% or bigger, image stand still), or slip (have more than 40 PCM frames which can’t self-correcting). Which terminal come out this thing is not fix, when the terminal call out, they usually use some channels on the MCU’s 2 different output ports.

Alarm Information

CRC verification bit error more than 80%; MCU alarm window inform “self-correcting delay”, but failed. 

Handling Process

  1. 4 channel conference test. Call 7 branch meeting place relative longer time in turn, then examine user’s switch and find all the meeting place using the first board. Add the 8th  meeting place( anyone of the rest) , last relative longer time, this meeting room has the biggest chance to come out above problem, examine switch and find the second board is being used 2 channel.
  2. 6 channel conference test. Call each branch meeting place in turn, almost find no problem
  3. 6 channel conference test. Call all the 6 branch meeting place at the same time, usually 2 branch meeting place come out the problem, but we can’t see more information about efficiency channel of the switch
  4. Change the calling strategy.  Former MCU has only one external number 177 ( inside number).  Let 5PRI from 1770 to 1774 respect, and provide each conference place a number. Change switch’s configuration, do 4 channels / 6channels conference repeat test, until each conference place uses only one board when branch conference place call in MCU, the problem will be sloved.

Root Cause

The switch PRI interface boards have difference between different users, but engineers of the customer can’t find out this reason.