This general purpose two-transistor complementary configuration was found in the December 1972 issue of Radio Electronics magazine. The power supply is between 6 and 12 V.
The automatic modulated siren circuit shown in the figure really produces an interesting sound...
This circuit was found in the August 1973 issue of Radio Electronics magazine. The Darlington...
This circuit has three settings, central sound frequency, modulation speed and modulation depth. The...