This sensitive circuit was found in the June 1995 Electronics Now magazine. R1 can be from 10k to 1M depending on the desired sensitivity. Power is supplied by the relay.
This limiting circuit with an operational amplifier has an adjustable cut-off point and can use...
This Japanese commercial transistor radio circuit was found in a 1967 documentation. The...
This voltage-controlled oscillator uses an integrated circuit not common today. It can generate...