This RF circuit measures transmission power from 0.25 W to 10 W. The maximum frequency depends on the diode and the gauge is an analog instrument. A multimeter can be used instead.
The Texas Instruments INA826S Instrumentation Amplifier Evaluation Module is available from Mouser...
This circuit is designed to activate an automotive alarm after 8 minutes of activation. Of course...
Figure bellow shows how the 4088 or 4018 can be used as a touch switch. Two metal plates separated by 1 mm...