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.
We found this chopper circuit in a 1967 publication. The transistors are of the time, and current...
This circuit was found in a 1977 Radio Handbook. The ports used are CMOS like 4001 and the...
Ohmite TGHD non Inductive High Power Resistors Available in SOT-227 enclosures, these Ohmite...