File:Marconi's Coherer Receiver at Oxford Museum History of Science (cropped).jpg

English: One of the first radio receivers, constructed by Italian radio inventor Guglielmo Marconi in 1896, on display in the Oxford Museum of the History of Science, UK. It used a coherer, a tube of metal filings, as a radio wave detector, connected to a wire antenna. The coherer is the glass tube on the right. When it detected a radio signal the resistance of the coherer would drop, and DC current from a battery would flow through it and turn on the relay in the cylindrical container at right, ringing a bell. This receiver was used by Marconi in his famous 1896 "black box" demonstration of radio communication at Toynbee hall, London.

Caption on card: "Coherer receiver by Guglielmo Marconi, 1896: Marconi used this device for a famous public demonstration of wireless in London's Toynbee Hall in 1896. At a public lecture by William Preece, chief engineer of the General Post Office, whenever Preece switched a transmitter and created an electric spark, a bell rang in a box Marconi took to any part of the lecture room. There was no visible connection between the two. The demonstration caused a sensation and made Marconi a celebrity."