1. An automatic communications switching system comprising a switching network for completing calls through the system, a data processing network for controlling the completion and supervision of calls through the system by the execution of programs, and a plurality of peripheral circuits interfacing between said switching network and data processing network to provide signals regarding the condition of the switching network to the processing network and for transmitting signals from the processing network for controlling and supervising the operation of the switching network, and in which said data processing network includes a first and a second processor, a first individual memory normally accessible only to the first processor for storing data including programs of a first set concerning calls being handled by said first processor, a second individual memory normally accessible only to the second processor for storing data including programs of said first set concerning calls being handled by said second processor, means in individual memories for storing address information of calls through peripheral circuits, the calls being handled by the processor associated with the respective individual memory, a further memory commonly accessible from both said first and said second processor for storing data representing conditions of said peripheral circuits being completed through said peripheral circuits under the control of both said processors in a load sharing manner and, in which each of said processors includes means to prevent said programs of said second set from being simultaneously executed by both processors to thereby give rise to conflicting situations due to the simultaneous handling of similar programs, said preventing means comprising a storage table individual to each processor, said table indicating the programs to be handled and not to be handled by the particular processor.