Wireless doorbell production circuit

Circuit working principle: The wireless doorbell button, together with the transmitter, is embedded
in the wall next to the door. The indoor receiving distance of the receiver can reach more than 10 m. The transmitter uses
a 9V laminated battery, and the receiver uses three AA batteries. The receiver's standby current is only
0.5 mA, and its operating current is 140 mA.
    Transmitting part: Figure 5-la circuit consists of A and B in the CD4069 six-inverter,
resistor R2, and crystal JT. and so on form a high-frequency oscillator, C, D, E, and F form the shaping
and driving circuit respectively , and the signal passes through the thyristor VT. Amplified, and then
emitted to the air after resonance with ￡:, C2 and C3 .
    Receiving part: As shown in Figure 5-lb, the external signal passes through the loop antenna and is received
by VT. and other components form a super regenerative detector, VT2, VT3, A, B, and c are used for
voltage amplification, VD3, VD4, etc. are used for large signal detection (this is designed for anti-interference),
and finally the detected signal passes through D, E, and F. Output square wave signals at pins 10 and 12 , triggering
pin 4 of the special doorbell chip KD-OA. At this time, the speaker will emit loud "ding dong
", "Hello, please open the door" and other calling sounds.