This circuit reminds the driver when he removes the keys from the ignition, leaving the lights on. The circuit is from an August 1974 Radio Electronics magazine.
This circuit uses a JFET CA3140 operational amplifier to convert a low frequency sinusoidal signal...
This commercial radio for the AM band was sold in Japan in the 1960s. The circuit has an IF of 455...
In the figure we have a simple way to produce tone in a piezoelectric transducer. The frequency depends...