The circuit claimed has a high movement sensitivity. Even air moving (hot air rising, wind blowing) will trigger it when the trimpot is set near the most sensitive position. The transmitter sends out a steady ultrasonic tone at 40kHz. At this frequency the wavelength is. This ci
rcuit will controls the initial frequency and controls how much the envelope follower responds to the input signal. An envelope follower/filter combination translates the typical dynamic properties of your axe into modulated timbral changes too, you could feel of it as an automatic wah-wah pedal. Independent Initial Frequency and Sensitivity knobs provide you with. This circuit is used to detect whether your phone line is active or not. Components List: R1, R2, R3 = 22M Ohms R4 = 2. 2M Ohms C1 = 0. 47uF/250V Mylar caps D1 = 1N914, NTE519, or other small signal diode Q1 = 2N3904, NTE123AP Q2 = 2N3906, NTE159 Q3 = IRF510, NTE2382, MosFet This kind of circuit. The following circuit diagrams are tone detector circuit diagrams which also known as sound activated switch circuit. Actually, these circuits use microntroller for switching because the circuits were designed for robot start up activation. But you can build switching module using relay. Tone Detector diagram 1 Tone Detector diagram 2 Tone Detector diagram 3 Tone. This is a very simple and easy build metal detector circuit, built based on a CS209A IC. The circuit will give surprising results and draws extremely small current from a 9 volt battery. It worked great on the Bench, But not so good outside for common metal detecting. But Definately a great circuit for sensing.