The Morris electronic telephone exchange

The Morris electronic exchange is providing dial telephone service in Morris, Illinois, U.S.A. It is an experimental installation which will serve about 600 customers during the trial period. The remaining customers in Morris are served by a No. 5 crossbar unit. In the electronic system, calls are switched through a space separation network using gas-filled diodes as cross-points. All control actions are performed by a central control unit consisting of transistor and diode logic circuits. Memory functions are centralized in a barriergrid store unit for temporary memory and in a flying-spot store photographic memory unit for semi-permanent memory. The system is controlled by a programme of instructions stored in the semipermanent memory. Major units are duplicated for reliability. Automatic trouble detection, trouble recording and trouble location features are provided. The system appears to offer two basic advantages which make important technical and economic gains possible. The first is the speed of electronic circuits, which allows centralization of basic functions and sharing of services of a given equipment unit. The second is stored programme control, which allows great flexibility in meeting the problems of growth, new services and changing requirements.