MULTIPLEXING DEVICE WITH ENCIPHERING FUNCTION

PURPOSE:To make deciphering a key difficult and to improve the secret strength by providing an enciphering function part for receiving a multiplexing signal on a high speed highway and enciphering only a signal of a time slot position to which plural low speed lines are allocated in accordance with the information of a line allocating function part. CONSTITUTION:A low speed line passes through low speed line use channel boards 201-203 and multiplexed by a multiplexing part 1 in accordance with contents 21 of a line allocating information use memory (line allocating function part) 2 in which line allocating information is stored, and allocated to each time slot (TS) on a high speed highway 11. As for a multiplexed signals 11, only a used TS is enciphered by used/unused time slot (TS) information 22 obtained from the memory 2, by an enciphering function part 3, and it is used as a multiplexing signal 31 to be sent out to a transmission line. By the signal 31, an oblique line part 31a, and a pear rind part 31b show an enciphered signal, and a signal of an unenciphered plain sentence, respectively. In such a way, deciphering by a tapper can be protected.