R-40-16 ultrasonic receiving circuit

The circuit is composed of VTl.~VT7 and other components. Since the signal received from the transmitter is very weak, the circuit uses multi-
  stage amplification to output a square wave pulse signal to control the working state of the bistable circuit composed of VT5, 1n and related components.
  Each time the transistor VT4 is turned on ( The transmitter transmits once) the trigger signal sends a trigger pulse to the bistable circuit via G and C, and VT5 and V;113 invert
  once . When VTfi; changes from cutoff to conduction, VT5 and VT7 cut off, and relay K is released and maintained. When the next pulse arrives, VT6
  changes from on to 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 .