TON KINSBERGEN / SCIENCE PHOTO LIBRARY TON KINSBERGEN / SCIENCE PHOTO LIBRARY
Early radio. Box containing electrical equipment for an early radio. The two rectangular objects at upper right are the batteries. An adjustable slide device is seen at lower centre. In the lid of the box, at upper right, is a device that is operated by a switch on the outside of the box. At left, on an extendable cord, is a headphone or speaker device. Other switches (centre) are labelled with amounts of resistance in ohms. Changing the resistance is one way of tuning certain types of radio circuits to different frequencies. The first radio communications were developed in the 1890s.
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