We found this receiver circuit for modulated light in a 90s Popular Electronics. Equivalent audio amplifiers can be used. Transistors are commonly used.
This circuit, in addition to transforming a sinusoidal signal into a square, shifts its phase. The...
This transmitter, found in Raytheon documentation from 1957, has a range of a few meters. L1 can...
This circuit uses operational amplifiers that must be powered by a symmetrical source to implement a...