| 摘要 |
PROBLEM TO BE SOLVED: To prevent the output of an image pickup indication by measuring a pseudo Doppler frequency and noise caused by an interference wave from another device by respectively counting and comparing an identifying frequency for modulating a transmission wave and an identifying frequency component which is taken-out from a received reflection wave by means of a second band filter through a mixer. SOLUTION: A signal inputted to the second band filter 14a interrupts a Doppler frequency, only the output frequency of an identifying signal generating circuit 16 is passed and inputted to a first frequency counting circuit 19a. Besides, the output of the circuit 16 is inputted to the second frequency counting circuit 19b and the respective frequencies are counted in the first and the second frequency counting circuits 19a and 19b. The respective counted values are compared in an identifying signal detecting circuit 18. When the counted values of the first and the second circuits 19a and 19b are mutually coincident, a state that the output of a photographing command is prohibited from the identifying signal detecting circuit 18 to a photographing command circuit 22a is released.
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