| 摘要 |
PURPOSE:To commonly use a center-to-automobile communication device to an existing ultrasonic car detector, by transmitting data through the AM modulation of a wave length of an ultrasonic car detector and making data with reception and demodulation by a wave reception head provided on a car. CONSTITUTION:An AM modulator 11 of an ultrasonic wave car detector consisting of a head 1 and a device main body 5 AM-modulates a pulse modulating wave at the pre-stage based on a coded transmission data from a center and the pulse is transmitted to the head 1 after amplification. The transmitted wave with this head 1 is reflected on a car 6 or a road 2 and received with the head 1. This received wave is amplified at a reception amplifier 13 and the timing between the transmitted wave and the reflected reception wave is controlled at a gate 14 and the propriety of detection of the car 6 is discriminated at a discrimination circuit 15. When the car 6 is detected, a detection pulse is outputted and transmitted to the center. Thus, data can be obtained by the car 6 by demodulating the received AM modulation. |
