BBC Radiola 'Bijou' crystal set Type 6, 1923. Made by British Thomson-Houston Co Ltd, Rugby. Serial No R23301.

This early crystal set radio features a transfer logo of the British Broadcasting Company with PO license number. The BBC had been established the previous year and manufacturers were required to obtain a license from the Postmaster General to produce wireless sets. The manufacturer acronym ‘BTH’ is painted in gold on the lid.

Crystal set radios employed a mineral crystal in delicate contact with a tiny coil of wire known as a 'cat-whisker' to detect broadcast signals. The cat-whisker had to be placed by the user in exactly the right position in contact with a fragment of crystalline galena. Not needing batteries, crystal sets used the power in the radio waves themselves to generate sound through the headphones.

When connected up to an aerial wire - about 100ft. being the recommended length - and a 20ft. long earth wire, the set was capable of receiving signals up to 30 miles from a BBC transmitter.

Crystal sets were a popular alternative to the more costly valve radios which required power to amplify the sound.