Ultrasonic remote control lighting switch circuit b

Ultrasonic transmitter circuit composed of T-40-16 and 555.
As shown in Figure a, the circuit consists of ultrasonic transmitter T-40-16 and 555 circuit. Adjusting the potentiometer RP can change the oscillation
frequency of the circuit. The 40kHz oscillation pulse output from pin 3 of the 555 drives the T-40-16 to work, causing it to emit a 40kHz ultrasonic signal. The working voltage of the circuit
is 9V, and the working current is 40-45mA. The control distance is greater than 8m.
    (2) The R-40-16 ultrasonic wave receiving circuit
    is shown in Figure 18-32b. The circuit consists of VT1-VT7 and other components. Since the signal received from the transmitter is very weak, the circuit uses
multi-stage amplification to output a square pulse signal, which is connected to VT5: VT6 and related components to form a bistable circuit. i. The transistor
VT4 is turned on every time Once (the transmitter transmits once), the trigger signal sends a trigger pulse to the bistable circuit via G and C. VT5:''VT6
reverses once. When VT6 changes from cut-off to on, VT5 and VT7 cut off, and relay K releases and holds. When the next pulse arrives
- VT6 turns on and turns off. VT7 is turned on and relay K is closed to control the load operation. This circuit can be used for remote control of various electrical switches
.