| 摘要 |
<p>PURPOSE:To prevent a malfunction without being interfered from external and internal noise. CONSTITUTION:Detection circuits 6, 7 receive signal currents whose frequencies are respectively f1, f2 passing through a band pass filter 1, the detection circuit 6 detects the signal current whose frequency is f1 and the detection circuit 7 detects the signal current whose frequency is f2 and they output a DC current. Block circuits 4, 5 receive an output of a band pass filter 1, the block circuit 4 blocks the signal current whose frequency is f1 and the block circuit 5 blocks the signal current whose frequency is f2 and they output a DC current. A control circuit 8 selects and outputs any of outputs of the detection circuits 6, 7, comparator circuits 9-11 compare outputs of the block circuits 4, 5 and the control circuit 8 timewise and in terms of levels respectively and a setting circuit 12 selects the output.</p> |
