This Integer32 object, part of a table index, defines the CID of a voice channel, which must match at both endpoints of a connection and is unique only within the context of a single Virtual Circuit. Because CID values are only unique per-PVC and not globally, an admin configuring multiplexed voice channels must ensure the CID matches on both ends of the call to avoid crossed channels. An engineer setting up a new voice channel over an existing PVC would assign this CID carefully, checking that no other active channel on that same PVC already uses it.