This circuit uses a resonant reed relay to recognize the frequency of an input signal. Adaptations can be made to obtain functioning as a shield. The circuit is from 1965 documentation.
In this oscillator a phase shift network formed by C1, C2, C3 and R1, R3, R4 determine the fase...
For inductive loads we have the configuration shown in the figure. Note that the optical coupler...
This circuit was found in the Linear Applications Handbook by National Semiconductor. It uses...