I found this circuit in an old documentation from 1982. The circuit can be assembled with the original integrated circuit 556 as well as with two 555, since the 556 is nothing more than a double 555. The transistor Q1 can be the BC548 and Q2 for greater power, without the need for R6 it can be the BD135. The circuit will operate at 6 to 12 V voltages and changes in C1 and C4 can be made to modify the produced sound.
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