Telecommunication systems with captive condition surveillance and release

Abstract

Subscriber stations in a telecommunication system are selectively connected and controlled by an exchange having a central control. The subscriber stations have operating conditions varying from an idle to a start condition and from a captive to the idle condition. Line connection circuits of the subscriber stations issue a signal indicative of a transfer of any subscriber station from the captive to the idle condition. Circuits common to the subscriber stations but separate from the central control monitor the subscriber stations as to the issuance of a signal indicative of a transfer of a subscriber station from the captive to the idle condition. Circuit components common to the subscriber stations and connected to the monitor circuits ascertain the particular subscriber station for which an indicative signal has been issued and carry out a release of the particular captive condition. The monitor circuit preferably monitors the subscriber stations also for a transfer from the idle to the start condition, and the system preferably is capable of issuing a corresponding request for a connection to the central control. The subscriber stations preferably are divided into groups for joint interrogation of transfer conditions, and may be subdivided into subgroups for individual interrogation of transfer conditions among the subscriber stations of a subgroup.