For many early radio listeners, purchasing a receiver which came with a loudspeaker was prohibitively expensive. Instead, they would listen to programmes through headphones. A crystal radio sets was a simple and cheap option. It consisted basically of a tuned circuit and a crystal detector, and had no batteries, the power delivered to its headphones all coming from the transmitter. Sterling manufactured headphones for use with some of the earliest commercial radios such as those produced by Marconi in the early 1920s.
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