Transparent dialing between interconnected telecommunication switching

Abstract

A multilevel data base memory structure for use by the processor control of each of a plurality of interconnected telecommunication switching systems so that communications between any two of the systems can be established with minimal interaction by the users. A comprehensive directory number plan provides for the allocation of blocks of at least one hundred directory numbers (i.e. 2400-2499) to the stations or features of each switching system. For those directory numbers serviced by a switching system the thousands/hundreds digits are utilized as addresses of locations of the memory structure first table level, the contents of which are pointers to various sections of a second table level. Within each such section the tens/units digits are used as addresses to define a location having stored therein an ultimate system function representative of, for instance; a standard call, conference call, speed dial . . . etc. For each block of directory numbers serviced by another system the dialed directory number thousands/hundreds digits are utilized as addresses of locations of the memory structure first table level which contain a quasi-ultimate system function which, when carried out by the system, automatically transfers the dialed digits via an interconnecting line to the switching system servicing the dialed number.