| 摘要 |
<p>PURPOSE:To enable an obstruction to be detected with simple constitution by using a transmitter and a receiver of microwaves and setting the directional characteristics thereof suitably. CONSTITUTION:If an obstruction exists in the part 13 where the directional characteristics of a transmitter 1 and a receiver 4 superpose, part of the reflected waves is received in the antenna 5 of the receiver 4. The microwave signal received in the antenna 5 is detected by a detector 6, is amplified by an amplifier 7 and is further compared with a reference voltage by a comparator 9. When the received level is higher than the reference voltage, an alarm is emitted from an alarm display device 10.</p> |
