English: A publicity photo of Italian radio pioneer Guglielmo Marconi posing in front of his early radio apparatus. The device at left is the transmitter, consisting of a Righi spark gap dipole antenna (balls) which is powered by high voltage from an induction coil (not visible). When sparks jump between the central metal balls, radio frequency oscillating currents are excited in the metal rod antenna, radiating radio waves. The device on the right is the receiver. It uses a primitive radio wave detector called a coherer (in box). When a radio wave from the transmitter strikes the coherer it becomes conductive. The coherer applies a pulse of DC current from a battery through a second circuit attached to the coherer to the mechanism at top, a telegraph sounder, creating a "click" sound. Information can be transmitted by turning the transmitter on and off rapidly with a switch called a telegraph key, spelling out messages in Morse code. The message can be translated from the series of clicks produced by the receiver. This early transmitter radiated radio waves at UHF frequencies, and its range was limited to a few hundred feet. Creator/Photographer: Unidentified.