| 摘要 |
PURPOSE:To automatically perform communication with a communication procedure control signal which is not ciphered irrespectively of whether or not a receiver is equipped with a cipher decoder, by including information indicating that whether or not the receiver is equipped with a cipher decoding device in the communication procedure control signal, and performing ciphered communication only when the receiver is provided with the decoder. CONSTITUTION:In response to a call from a transmitter 1, the circuit between the transmitter and a receiver 2 is connected and the transmitting function and receiving function of the transmitter 1, and receiver 2 are mutually confirmed. Then a control signal outputted from a communication controlling circuit 5 is inputted into the signal input terminal 22 of the receiver 2 from a signal output terminal 23 through the circuit without being ciphered and further inputted into a communication controlling circuit 13 without passing through a decoding circuit 16. A receiving function discriminating signal including information indicating that whether the receiver 2 is equipped with a cipher decoding function or not, is transmitted from the communication controlling circuit 13 to the transmitter 1. Upon receiving the discriminating signal, the communication controlling circuit 5 of the transmitter 1 sends a mode setting instruction signal including information indicating that ciphered transmission is performed as the response. When the information indicating that ciphered transmission is performed is included in the mode setting instruction signal, the communication controlling circuit 13 of the receiver 2 controls a multiplexer 15 so as to select the output of the decoding circuit 16. |
