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.
The oscillator shown generates a rectangular output signal at a frequency of 5 MHz, determined by the...
Found in a Popular Electronics - January/February 1969 this circuit was intended to increase the...
Found in a radio amateur magazine of the 1980s, this circuit uses components that can still be...