Relays up to 100 mA can be driven by the 555 with the recommended circuit. The circuit is from an article in the September 1992 Radio Electronics magazine.
This circuit recognizes a tone determined by the tuned input circuit (R3 / R4 / C2). The circuit...
This CMNOS crystal-based circuit generates a 2 Hz signal. It was found in the October 1994 issue of...
This is one of the possible configurations using the LM139, 239 or 339 voltage comparators. The...