This attribute indicates what is current internal B-channel state. The attribute may have the following values for any supported access signalling protocol on Passport: unknown, the B-channel has not registered yet for SigChan services maintB, the B-channel is undergoing a maintenance action idle, the B-channel is available for ingress/egress calls busy, the B-channel is currently being used for an ingress or egress call ingress, the B-channel is currently being used for an ingress call (from the external network to the subnet) egress, the B-channel is currently being used for an egress call (from the subnet to the external network)

In addition, CCS protocols supporting SERVICE messaging may also use the following values: idleMaintenance, the B-channel received a SERVICE message placing the channel in maintenance, and no calls are active on the channel ingressMaintenance, the B-channel received a SERVICE message placing the channel in maintenance, and an incoming call is active on the channel egressMaintenance, the B-channel received a SERVICE message placing the channel in maintenance, and an outgoing call is active on the channel outOfService, a SERVICE message to or from the PBX has placed the channel out of service