COMMUNICATION SYSTEM FOR CONTROL SIGNAL

PURPOSE:To attain the control for any terminal equipment by ciphering a control signal as required in the operation of a power distribution system or not ciphering the signal for the transmission reception. CONSTITUTION:A sales office 1 is provided with a master station 2, a general terminal data generating section 4 and a mixer section and connected to a slave station 8 via a common use 2-way transmission line TL. A control section 2a of the master station 2 discriminates whether or not a control signal is to be ciphered and ciphering processing 2f or non-ciphering processing 2d is applied to a control signal in response to the result of discrimination. Furthermore, the control section 2a adds display data representing whether or not the control signal is ciphered to the control signal and sends the result. A control signal decoder 9 in the slave station 8 detects display data from the received control signal and discriminates whether or not the control signal is ciphered based on the data. Then the decoding algorithm is decided in response to the result of discrimination and the original control signal is extracted by the algorithm.