This circuit generates short pulses. The transistor can be a 2N2222 or BC548 and the frequency is given by the resistors and the capacitor that can be changed.
We found this circuit in a 1986 publication. However, as it is based entirely on 555 integrated...
We found this circuit in a Poptronics from 1998. The circuit can be extended to more competitors...
In this circuit a 12 V lamp or LED blinks with the music signal applied to the input. R depends on...