ultrasonic receiver for headphones

Before going on to describe the circuit of the receiver, there is one point worth noting. Although primarily intended for use in an ultrasonic transmission system, it is in fact much more flexible than one might think. If the ultrasonic transducer is replaced by a suitable (i.e. tunable) LC circuit, a highly sens1t1ve `conventional` AM receiver is ob-tained. The circuit can also be usefully employed as a direction finder in the 10 kHz to 30 MHz region.