Infrared light signal receiving circuit

The receiving circuit of infrared light signal is shown in the figure. The circuit is mainly composed of operational amplifier IC1 and phase-locked loop integrated circuit IC2. The infrared light signal emitted
by the infrared transmitting circuit
is received by the infrared receiving diode D01 and converted into an electrical pulse signal. The signal is amplified by the ICI integrated operational amplifier and input to the phase-locked loop circuit IC2. This circuit consists of R3 and C7 to form an oscillator with a fixed frequency, which is the same frequency
as the transmitter circuit . cs and C6 are filter capacitors. Since the oscillation frequency of the Icl output signal is
the same as the oscillation frequency of the phase-locked loop circuit IC2, the @ pin of IC2 outputs a low level. At this time, the transistor Qol is turned on, the relay Kl is closed, and its contact can be used as a switch to
control controlled load. When there is no infrared light signal being emitted, the ⑧ pin of IC2 is high level, Qol is in cut-off state, and the relay will not work.