Found in American documentation from the 90s, this circuit uses a high voltage relay and has no grid isolation. The high values of R1 and R2 prevent the shock when it touches the sensors.
Found in an old documentation about neon lamps, this circuit has the frequency basically...
This simple standing waveform (ROE or SWR) meter is used to adjust antenna matching with...
This is the traditional configuration of a high-pass filter with an operational amplifier, such as...