A PRI endpoint port’s B-Channel logs a warning alarm when it is placed in a Maintenance/Far-End or Out-Of-Service/Far-End state. While in such a state, the port is unusable for calls to the terminal adapter. However, the user can still use the other remaining ports in the PRI endpoint to make calls to and from the terminal adapter. When a warning alarm is raised, use status pri-endpoint extension to determine the exact state of the port. Other alarms can be diagnosed by using the short and long test sequences. Note that a PRI endpoint port’s B-Channel can be placed in a far-end service state by direct action by the far-end terminal adapter or by inaction of the far-end terminal adapter. For example, if it does not respond to a Remote Layer 3 Query, see Remote Layer 3 Query Test 637 (for ISDN-PLK) the associated PRI endpoint port’s B-Channels will be placed in the Maintenance/Far-End service state.

A PRI endpoint port is a port on a UDS1 interface circuit pack and thus depends on the health of the circuit pack for proper operation, see the following figure PRI Endpoint Port Interactions. A problem on the associated ISDN-LNK’s (ISDN-PRI signaling-link port’s) D-Channel can also affect the PRI endpoint. In turn, the ISDN-PLK depends on the SYS-LINK (system link) to the packet interface. Keep this hierarchy of dependencies in mind when diagnosing problems.