This read-only counter reports the number of voice calls currently active at a specific subscriber voice end point at the moment it is polled, indexed by that end point's unique system-wide index. Since a subscriber end point typically supports one or a small number of simultaneous calls, this value is mainly useful for confirming current call state or session accounting for that specific line. An admin checks this alongside the completed/blocked counters to build a full picture of one subscriber's calling activity.