In all the houses exist the bells in the door. All want, they have the possibility of being possible to change the intensity, the tone of sound. With this circuit we have this possibility. With the materials round the gates, we can change the sound.
For the materials that exist in the circuit the frequencies are roughly 5 KHZ and 2 KHZ. The circuit functions only for small time interval afterwards the pressure of switch. Simultaneously with the sound we have also optical clue from LED D2. Changing the capacitors C2-C3, with different price of capacity, we create new sounds.
R1=470Kohm C1=22uF 25V Q1-3= BC 550
R2=22Kohm C2=470uF 25V Q2= BC 560
R3=3.9Kohm C3=1 uF 25V BATT=4X1,5V or external pack 6Vdc
R4-5=330 ohm D1=1N4001 SP= Speaker 8R /0,5W
R6=2.2Kohm D2=LED RED 3mm
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