In this assignment, the bit error rate (BER) of a double PCM communication system transmitting on a basic bands will be studied theoretically and with the help of Monte-Carlo computer simulation. In the system, P0=1/2 and P1=1/2 contingent and 0 and 1 bits are transmitted respectively with the help of +1V and -1V amplitude marks through cumulative channels. The mark at the entrance of the decision circuit of the receiver is r = ±1 + n