What is probably the cause for appearance of alarm, PCM asynchronization or unusable channel state on the end of PBX when it connects to Synway E1 boards?
If the remote PBX alarms during its connection to Synway E1 boards that there is a block at the board end which causes failure in calls or the PBX shows with instable PCM synchronization or unusable channel state, this is probably because of improper CRC-4 setup. CRC-4 is used to perform a cyclic redundancy check of multiframe signals, viewing if there is something wrong with the multiframe transmission. The driver sends the CRC-4 package through Timeslot 0 and the configuration item CRC-4[i] determines if the package is opened or closed. 0: Closed; 1: Opened (default). The driver does not do any thing about the CRC-4 package passed from the remote PBX. The effect of the CRC-4 check switch on E1 lines are as follows. 1) The remote PBX asks the Synway board to send CRC-4 but the board does not. Then the PBX gives the alarm information saying it fails to make normal calls. In such case, the channel seems to stay in idle or other states which are all not true. 2) The remote PBX does not a
