SBS trunk group members achieve in-service status without requiring any associated VoIP services to be in service.. All that is required for an SBS trunk group member to be usable for a call is that the associated signaling group reach an in service state.

When a SBS signaling group goes out of service for any reason, the associated SBS trunk group members associated with that signaling group are taken out of service to avert failed call attempts. Reasons that a signaling group might be taken out of service include busy out of the signaling group, or procr board removal or failure.