System for establishing telephone connections or the like in networks which may extend over several territories

摘要

686,165. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. April 8, 1949 [June 17, 1948], No. 9591/49. Drawings to Specification. Class 40 (iv). In an international automatic telephone system, a calling number (e.g. B15 ANT 3327) consisting of a territorial code digit B and local digits is registered at the calling exchange and the territorial code and local digits are transmitted by the register in response to distinctive proceed-to-send signals Y, X returned by registers at forward exchanges. When, at any stage, an exchange is selected for tandem operation, a territorial selector is seized by a voice-frequency signal CY from a register at the preceding exchange. A proceed-to-send signal Y is then returned to the calling exchange which transmits the territorial code digit. The code digit B is transmitted again and again from the calling exchange as the proceed-to -send signal Y is returned by successive exchanges. When the connection is extended to an exchange in the territory denoted by B, a local selector is seized by a voice-frequency signal CX from a register at the preceding exchange and a proceed-tosend signal X is returned. The local digits are then transmitted from the calling exchange. The registers used in successive tandem exchanges drop out as the connection is built up. In a modification, a single seize signal is used for all calls and is followed by the territorial code. The forward exchange uses the territorial code to discriminate between local calls and tandem calls. In a further modification, the territorial code is transmitted alone. Alternative routing facilities are provided in the system described. Specification 645,303 is referred to.