Circuitry for providing executive ringback in a PBX system in accordance with a supplied class of service

摘要

In a telephone switching system wherein a plurality of line circuits are terminated in station sets, the line circuits are interconnectable to a plurality of trunk circuits through a multistage switching network. A call originated by a calling party to a called party, engaged in a conversation with a third party, is automatically completed at the conclusion of the conversation between the called party and the third party by ringing back the calling party and the called party provided both parties are equipped with a class of service which permits executive ringback. The ringback feature is initiated by the calling party upon receipt of a special busy signal by a flashing of his switchhook.