This circuit is able to repel the rats and mosquitoes. The frequency produced is between 30kHz-50kHz, and can be changed according to the frequency needed. Here is the schematic : This circuit uses piezo tweeter which is able to produce sound with high frequency without disturbing any human being. Estimated price : $10 Component list [...]
The following circuit serves as an additional indicator to the fixed telephone, and can be put in any room. This circuit helps the homeowner when there is a phone call. This circuit needs to be connected in parallel with the telephone cable. It doesn’t need the power supply since it uses the voltage available in [...]
This circuit will produce sound similar to police siren using astable multivibrator mode of IC timer 555. This circuit is controlled by 2 timer ICs and 2 resistor variables. First IC timer will produce 1 Hz frequency which will increase and decrease periodically. The second IC timer serves as periodic ON/OFF switch. VR1 has a [...]
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