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.
CRC verification bit error more than 80%; MCU alarm window inform “self-correcting delay”, but failed.
The switch PRI interface boards have difference between different users, but engineers of the customer can’t find out this reason.