Human hand sensor alarm circuit

The circuit shown is a human hand induction alarm circuit, which is
simple and practical. When a person's hand is close to the induction line, the alarm will
sound. This is very suitable for Yang Electric's anti-theft alarm.
    The induction wire L is a wire with a length of lo~50cm. If the wire
is too long, it will cause the alarm to alarm itself. When a human hand approaches the induction line L, a signal
will be induced on L , and the signal is added to the ② and ⑥ pins of the time base circuit NE555. Since the input impedance of ② and ⑥ pins is very high, even a weak induction signal will It will make 555 work, and the stronger signal on pin ◎ will drive the speaker BL to make sound.   The alarm is very sensitive. When the human hand is 15cm away from the sensing line, the alarm will sound silently and disappear after 1 minute.