| 摘要 |
PROBLEM TO BE SOLVED: To remove wire between telephone communication terminal equipment and an exchange device and to improve privacy and noise resistance by setting a radio channel, by means of spread spectrum communication between terminal equipment and the exchange device. SOLUTION: A preamble signal which is spread spectrum-modulated is received by the antenna 500 of exchange devices 200/300 from terminal equipment. For example, the synchronizing circuit 214 of a No.1 modulation/demodulation device 210 is operated, and it synchronously acquires the signal. A central controller 240 sets the down preamble code and the PN code of terminal equipment in a PN code generator 213 for the spread modulator 211 of the No.1 modulation/demodulation device 210. The down preamble signal is transmitted through the antenna 500. Call terminal equipment switches the spread spectrum code of an up line to the PN code for communication from the preamble code and sends a switch signal. In the exchange device 200, a down line is switched to the PN code for communication. Then, the line between terminal equipment and the exchange device 200 is set. |
