This well-known circuit version of the siren was obtained in a Colectro Handbook from the 70s. The transistors are of general use, with Q2 being a BD136 for greater power with power from 6 to 12 V.
This is the basic operational amplifier configuration for gain 10. R2 can be changed to other...
This interesting circuit was obtained from a 90's EDN. What it does is generate negative voltages...
This circuit is from an English magazine from 1976. By replacing the transistor for a BC548, the...