Melody Doorbell circuit

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.
Melody Doorbell circuit - schematic

Part List 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 R7=1.2Kohm IC1=7413 All Resistors is 1/4W 5%

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