We found this circuit in the April 1978 issue of Radio Electronics magazine. The 2-digit circuit uses common TTL integrated circuits and must be powered by a voltage of 5 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...