This circuit is used to sense temperatures in degrees Celsius and Fahrenheit. The circuit is from Special Projects from 1983 in Radio Electronics magazine.
This Japanese radio is from the 60s, presenting excellent sensitivity and an output power of 100mW...
Found in a Popular Electronics from the 90s, this circuit uses components that are still current....
This circuit consists of a simple capacitance bridge. The handset can be high impedance from 500...