Universal remote control switch circuit

Circuit working principle: The circuit
consists of a power supply part, a sending part and a receiving part. The power supply is 5v DC voltage that is stepped down, rectified and stabilized by 7805 from the mains. The transmitting part (Figure a) is a monostable circuit formed
  around the NE555 timer ( IC
.). It uses two infrared light-emitting diodes (LEDs) to emit infrared light.
Use RP to set the output frequency of IC4 to 38 kHz. The transmitter part is powered by a 9V battery
.
  The receiving part (Figure b) consists of infrared detector TSOP1738 (IRX.),
timer NE555 ( IC 2), counter CD4022 (LC3) and some discrete components
.