In the figure we have a way of receiving ultrasonic signals of a single frequency using a PLL 567. The circuit is from Radio Electronics from November 1985.
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...