Beam telephone

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The Infraphon is a light beam telephone that transmits conversations with the help of infrared rays . This technology was intended to bypass the license for radiotelephony , which was still required in the mid- 1960s , since CB radio was not yet available.

Working method

The transmitter consists of a light bulb, the filament of which sits in the focus of a parabolic mirror. The bundled light beam is thrown against a mirrored membrane. When the membrane is discussed, the light rays vibrate. If they hit the parabolic mirror of the receiving device, this signal is converted back into an audible signal with the help of a photo resistor and a transistor amplifier.

Problems

Since the light beams have to go directly from the transmitter to the receiver, such a "telephone" can only be used within sight and only up to approx. 500 m. The light beam must also hit the receiver as precisely as possible in order to ensure usable transmission quality. For these reasons, this technology never caught on and was quickly forgotten.

literature

  • Wollmann: The light beam telephone . The New Universe 83, pp. 334-340.
  • H. Papousek, Uwe Jürgens, Mechthild Papoušek (eds.): Nonverbal Vocal Communication. Comparative and Developmental Approaches, Cambridge University Press, Cambridge 1992, ISBN 0-521-41265-X .

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