Overflow alarm circuit

The overflow alarm can prevent the water from overflowing when filling the water tank of the washing machine and the shower water tank,
and the boiling water from overflowing when the kettle is boiling water. This overflow alarm has a simple structure, is easy to make, and is low in cost
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    The picture shows the working principle diagram of the alarm.
    It is a complementary self-excited oscillator composed of VT1 and VT2. This kind of alarm
can be made with only two transistors, a resistor, a capacitor and a speaker. Since they all use germanium tubes, they can operate at a low level. Works at an operating voltage of 3V.     The probes of the overflow machine and shower water tank are composed of two metal wires. When using, just place the probe in the washing machine barrel (or water tank).