GB1218902A - A method of hunting free connection paths in a telecommunications network - Google Patents

Abstract

1,218,902. Automatic exchange systems. SIEMENS A.G. 28 March, 1969 [29 March, 1968], No. 16355/69. Addition to 1,176,514. Heading H4K. In a multi-exchange system in which the number of the called party is transmitted throughout the system until the exchange to which he is connected is found whereafter a path back to the originating exchange is set-up using route identification data supplied by each transit exchange, certain subscribers are allocated to a local exchange, whereby for such subscribers it may be sufficient to transmit initially through the system only the three digits of the local exchange code. When the main exchange, e.g. A, having the wanted local exchange, e.g. ZV1, connected thereto is found, a path back to the calling exchange is set up and the remainder of the wanted number is sent to the local exchange directly. If, however, the wanted number is sent with the local exchange code during initial route finding it can be immediately used, once the correct main exchange is found with the aid of the local code, to determine the free/busy state of the wanted party, whereby undue holding of the backward path is prevented. Certain privileged subscribers, e.g. 111, 112, may have three digit codes so as to allow them to be found more readily. A local exchange, e.g. ZV2, may be subdivided and each subportion ZV2a, ZV2b allotted to a different main exchange D, F. In this case if a call for subscriber ZV2b 999 should reach D before it reaches F, it is immediately rerouted to F with the aid of a routing instruction supplied by ZV2a.