| 摘要 |
PURPOSE:To prevent the misperception of a passer-by for a visitor while reducing power consumption by trimming the oscillation of an ultrasonic pulse intermittently. CONSTITUTION:The supply of power to a transmission circuit 1 and a receiving switch circuit 6 is done through a transistor Tr and contacts B and A of a switch SW. The driving of the transistor Tr is turned ON or OFF according to the oscillation output of an intermittent oscillation circuit 12, which comprises a mono-stable multivibrator 13 comprising inverters I1-I3, resistances RS and RT and a capacitor Cr, a D flip-flop 14 and an AND gate G1. The oscillation frequency TC of the non-stable multivibrator 13 is determined by TC=2.2CTRT. |
