ISDN D channel protocol error
A protocol error occurred on the ISDN D channel. The D channel carries the signalling for ISDN trunks. The D channel protocol is designed to be able to recover from protocol errors.
If this error occurs frequently it may indicate a problem with Blueworx Voice Response. Check the error log for other errors by the ISDN signalling process; this may identify the origin of the error. There are several steps you can take to attempt to solve this problem. Check that the configuration of Blueworx Voice Response matches the network configuration. If they do not match, stop the ISDN signalling process using the Custom Server Manager. Reconfigure Blueworx Voice Response to match the network, then restart the signalling process and re-enable the trunks.
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Log, System Monitor