| 摘要 |
<p>PURPOSE:To prevent that a detecting signal of an object in water is erroneously output by dissolving an output signal of a wave detector into a plurality of narrow frequency bands, obtaining the difference of the average value of detecting outputs and the detecting value of each narrow frequency band, and shutting a subject switch circuit when the difference is not smaller than a predetermined value. CONSTITUTION:Sounds generated from an object 9 in water are detected by a wave detector 1 and converted to electric signals. The electric signals are dissolved into an optional number of narrow frequency bands by a frequency dissolving circuit 2 and detected by a wave detecting circuit 3. In the case where a switch circuit 6 is connected, the average of the detecting output signals of the number connected by an average calculating circuit 4 is calculated. Thereafter, the difference of the detecting output signal at a point connected by the switch circuit 6 from the average output value of the average calculating circuit 4 is calculated by a difference calculating circuit 5. If the output of the difference calculating circuit 5 is not smaller than a preset value, the switch circuit 6 connected to the output of the wave detecting circuit 3 is shut by a switch controlling circuit 7.</p> |
