Infrared anti-theft alarm circuit

Circuit working principle: C3, C4 and their external resistors and capacitors form an oscillation circuit
with an oscillation frequency of about 40 kHz . C1 and C2 generate oscillation signals of tens of hertz and control the oscillation circuit composed of C3 and C4. When pin 4 of CD4011 is at high level, the oscillation circuit composed of C3 and C4 starts to oscillate; when pin 4 is at low level, the oscillation circuit composed of C3 and C4 stops oscillating.