| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical transmitter-receiver capable of executing communication with a mobile object traveling at high speed while keeping compatibility with conventional equipment by receiving an optical transmission wave modulated at two kinds of modulation speed and automatically recognizing the modulation speed of the optical transmission wave. SOLUTION: When an optical vehicle sensor 10 is installed on an expressway, down link information modulated at high speed is sent out. An on-vehicle optical transmitter-receiver 21 is provided with a 2nd modulation speed recognizing part 13 and a 2nd modulation speed switch part 17 to be correspondingly operated. When low-speed modulated down link information is inputted from a conventional vehicle sensor on a general road, high-speed modulated up link information is sent and when high-speed modulated down link information is inputted on the expressway, high-speed modulated up link information is sent. A reception view angle is extended so that this vehicle detector 10 can deal with a vehicle mounting the conventional on-vehicle optical transmitter-receiver and when such low-speed modulated up link information is received, the modulation speed of the down link is switched to low. |
