ELF Monitor (CB21055E)

This circuit monitors extra-low frequency (ELF) fields. We found it in an American documentation from the 90s.

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fet infrared Modulator (CB14681E)
The circuit shown is from the Texas Instruments optoelectronics manual, applying to low power...
High Impedance 2 W Amplifier (CB6163E)
This circuit was found in a 1968 General Electric documentation. It has an input impedance of 2 M ohms...
Twin-T Rejector Filter 741 (CB25603E)
This filter that rejects a frequency range determined by the double-T was found in the August 1993...