This circuit was found in an Electronic Design. It makes use of a relaxation oscillator to trigger an SCR and two relays. The circuit operates at frequencies of 12 to 180 cycles per minute.
This circuit uses a Hall device from that time as a sensor. The circuit is from an English...
Found in Radio Electronics from the 90s, this siren finds many variations on this site. The...
This audio generator that produces both rectangular and sinusoidal signals was found in a...