At the sending end randomly generated binary code number signals are inserted into predetermined lines of the vertical retrace interval. The code number signals are also processed in accordance with a program assignment code to change or leave unchanged a predetermined characteristic of the television signal. Periodically, program identification signals, each signifying a program identification number, are inserted into the television signal instead of the binary code number signals. At the receiving end, the program identification signals are utilized to address a random access memory which furnishes program assignment signals. The program assignment signals control logic circuits to process the code number signals in accordance with the same program assignment code utilized at the transmitter. The output of these logic circuits is then utilized to decode the received encoded signal. Further, means are furnished to record the program identification number in the random access memory at the receiver for billing purposes, if the subscriber indicates acceptance of the program. Both this recording and the decoding of the encoded signal are impeded if a catagory switch at the decoder furnishes a catagory selection number which does not correspond to a catagory selection number inserted into the encoded television signal at the transmitting end.