Here is the real deal. My starting point. Everything requires energy to operate. The On/Off is defined within a limit. for example if between 3 and 5 v it is on if less then 3 volt its off. A morse code concept. I am working on a thermometer so I need to make or buy a sensor. Then I need to calibrate it. Translate the signals from signal no signal or strength of signal to a temperature. This is where I am now.
