摘要 |
PURPOSE: To reduce the load of an upper layer protocol and to execute quick system control by transmitting and processing system control information such as an information transmission speed and address information by a modulation- demodulation circuit level. CONSTITUTION: When an information transmission speed is high, a transmitting station sends a signal PNO modulated by a symbol '1' e.g. to a preamble to be sent, and when the information transmission speed is low, sends the inverted signal of the signal PNO moduled by a symbol '-1' to the preamble. On the other hand, a receiving station discriminates the polarity of the preamble by a timing pulse generated when information transmission is started after establishing code synchronization. When the symbol of the preamble is '1', high information transmission speed is judged, and when the symbol is '-1', a low information transmission speed is judged. Clocks generated from a high speed clock generator 201 and a low speed clock generator 202 are switched by controlling a change-over switch 203 and an information signal clock is supplied to a parallel/serial converter 104. |