PURPOSE: To prevent the crosstalk of a mobile car due to simultaneous and malfunction with signals other than those at a fixed terminal, by attaining nondirectivity of an ultrasonic wave transceiver of the mobile car by means of the unidirectional constitution of an ultrasonic wave transceiver at the fixed terminal.
CONSTITUTION: A signal from a fixed terminal code generator 21 is transmitted from a transmitter 22 to a mobile car 4. The fixed terminal code of a reception signal of a mobile car ultrasonic wave receiver 41 is discriminated by a discriminator 42, a generator 43 adds a code specific to the mobile car only when the codes are coincident and transmits the code from a transmitter 44 to the fixed terminal 2. The terminal 2 supplies the reception signal of a receiver 23 to a central processing unit 1. In this case, the directivity 50 of the transmitter 22 and the receiver 23 is designated as unidirectionality, and the directivity 60 of the transmitter 44 and the receiver 41 is designated as nondirectivity.
ISHIHARA KENICHI
WATANABE TAKE
KONDOU KIKUO
MIYASHITA TAKAO
HANMURA HISAO
