Illustration of Hot wire barretter

1902 Hot wire barretter

The book of science

Tom Sharp

Reginald Fessenden electromagnetism Illustration of Hot wire barretter

Hot wire barretter

For receiving AM radio signals, Reginald Fessenden ran a current across a thin platinum wire heating it almost to the point where it lost its ability to conduct. Adding an AM signal to the current increased the temperature when the amplitude rose stopping the flow of electricity and decreased the temperature when the amplitude fell letting the electricity flow.


The barretter acted as a rectifier for an oscillating AM signal. The amplifier had not been invented, so listeners were wired to earphones.

Effects of heat

Heat me sufficiently and I’ll stop trying; sleepiness overtakes me till thinking stops. It’s useful to know one’s limits; biology opens sweat glands and regulates the heart. Add ice to the lemonaide; pour me a beer; there’s a lot I still want to figure out.