In-Service (INS)

The B-Channel is in its normal operating state.

Out-of-Service/Far-End (OOS/FE)

A B-Channel is initialized to this state when first administered. The switch then sends messages to the far-end terminal adapter to negotiate the B channel into service. If the far-end terminal adapter does not respond to the messages within a certain time period, the port remains out of service, and maintenance will periodically resend the messages. The port is unusable for incoming and outgoing calls, although other ports in the PRI endpoint can still be used.

Out-of-Service/Near-End (OOS/NE)

This is the state of the port when a hardware failure exists on the signaling link, the NPE Crosstalk test fails, or when the port is busied out by command. In this state, the port is unusable for calls coming into the switch or going out to the terminal adapter, although other ports in the PRI endpoint can still be used for incoming and outgoing calls. No messages are sent to the far-end terminal adapter until the signaling link comes back into service or the port is released by command.

Maintenance/Far-End (MTC/FE)

This state is reached when the far-end terminal adapter does not respond to messages sent over the signaling link for a particular port within a certain amount of time. This state is different from OOS/FE since the signaling link must have initially been up and the B-Channels in service. The switch will periodically send messages to the far-end terminal adapter to try to negotiate the port B-Channel into service. The port is unusable for outgoing calls to the terminal adapter but will service incoming call requests from the far end. Other ports of the PRI endpoint can still to place outgoing calls to the terminal adapter. Transitions into MTC/FE do not drop stable calls. If the service state changes from in-service to MTC/FE, stable calls are unaffected.

Maintenance/Near-End (MTC/NE)

Use busyout, test port l or test pri-endpoint l to busy out the signaling link (SYS-LINK). Transitions into MTC/NE do not drop stable calls. The busyout link lnk-no command does not drop stable wideband calls. In this state, the B-Channel is not usable for new incoming calls to the switch or new outgoing calls to the terminal adapter.

Pending States (PEND)

If the near end is expecting a timed response from the far end for a request to change the service state of a port, apendingstate is in effect. For example, if the port is out-of-service/far-end and an in-service message was sent to the far end, then the service state of the port is OOS/FE-PEND/INS meaning out-of-service/far-end, pending/in-service. The service state will reflect this pending state until the far end responds or the timer expires.