| 摘要 |
PURPOSE:To prevent erroneous operation due to electric noise or the rising in temp. of a background, by adding a time circuit for holding the output of an increment judge circuit or a decrement judge circuit for a definite time. CONSTITUTION:When an invader to be detected enters a detection area, the output of L1 shown by AM in the drawing appears in an amplifier 2 by the output of a detection element 1 and pulse like output shown by is issued from an increment judge circuit 3 while output extended to a definite time shown by T1 is issued from a timer circuit 5. When the invader exited from the detection area, pulse like output shown by and output extended to a definite time shown by T2 are issued. The logical product conjugation of both outputs is outputted as shown by AND to come to alarm output. The increase of a heat ray due to the rising in circumferential temp. is shown by TE and, because there is no decrement in the output of the amplifier 2, no output is obtained within the time of the timer circuit 5 and no erroneous operation is performed. Further, only the output of a decrement judge circuit 4 for a slight time shown by is issued to electric noise shown by NO and no erronous operation is caused. |
