This simple tone control using two transistors was found in an Electronics Today International of the 90s. Transistors are general purpose NPN types, like the BC549 for greater gain.
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...