This basic circuit showing the LM3914 “inside” was published in the October 1980 issue of Radio Electronics magazine. Note that R1 determines the brightness and that the power supply is 9 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...