This circuit was described in an article in the February 1993 Radio Electronics magazine. The frequency depends on the crystal and L1 is optional.
Found in Radio Electronics magazine from June 1968, this circuit produces signals from 30 Hz to...
This circuit reminds the driver when he removes the keys from the ignition, leaving the lights on. The...
T Found in a 1992 Popular Electronics, this sophisticated circuit uses two speakers on a different...