EXCLUSION SYSTEM FOR A KEY TELEPHONE SYSTEM

摘要

The exclusion system is employed with a central office/ private branch exchange (CO/PBX) system and a party line paging and intercom system. A first circuit is coupled to the "A" lead of the party line system, and is responsive to a predetermined potential on this "A" lead to couple a tip conductor and a ring conductor of an associated subset of the party line system to the tip and ring conductors of a selected one of the CO/PBX system and the party line system. A second circuit is coupled to the "A" lead of the party line system to manually generate a first exclusion potential for the party line system to exclude subsets not already connected to the party line system. A third circuit is coupled to the "A" lead of the CO/PBX system and is responsive to a given potential on this "A" lead to automatically produce a second exclusion potential on this "A" lead to exclude subsets not already connected to the CO/PBX system.