AN APPARATUS FOR CONNECTING A FIRST PBX OR PABX COMMUNICATIONS SWITCHING SYSTEM TO A SECOND PBX OR PABX COMMUNICATIONS SWITCHING SYSTEM

摘要

In order to expand or increase the number of lines of a communications system, this disclosure enables connection of one PBX switching system to another by connecting the switching networks to junctors which establish a multichannel transmission link between the first PBX module and a second module of similar format. The junctor is treated internally in each PBX module as a line or trunk port and whenever an extension number which is not contained in the numbering plan of the individual module is dialed, the control unit of the PBX will direct that call to any free junctor. The complete dialed number is transmitted from the originating module via the junctor to a receiving junctor at the other switching system. The dialed number is received at the receiving junctor through the established communications path between junctors for channel associated signalling or through a common signalling channel through which signalling for all other junctors in the link is transmitted, and after synchronization, it is utilized to made a connection between the called terminal and the calling terminal via the control unit located at the second switching system. The unique use of junctors to connect PBX systems allows for the initial installation of a small system at low cost which system can be expanded in the field in a cost effective manner by merely adding on additional systems. The distance between systems and subscribers in a system has little or no effect on its performance.