In the 19th century, telegraph and telephone engineers had recognized the need to extend the distance that signals could be transmitted. In 1906, Robert von Lieben filed for a patent for a cathode-ray tube which used an external magnetic deflection coil and was intended for use as an amplifier in telephony equipment. This von Lieben magnetic deflection tube was not a successful amplifier, however, because of the power used by the deflection coil.F. B. Llewellyn. (Mar. 1957). "Birth of the Electron Tube Amplifier". New York: Ziff-Davis. Radio & Television News. p. 44 Von Lieben would later make refinements to triode vacuum tubes.
In the 19th century, telegraph and telephone engineers had recognized the need to extend the distance that signals could be transmitted. In 1906, Robert von Lieben filed for a patent for a cathode-ray tube which used an external magnetic deflection coil and was intended for use as an amplifier in telephony equipment. This von Lieben magnetic deflection tube was not a successful amplifier, however, because of the power used by the deflection coil.F. B. Llewellyn (Mar. 1957). "Birth of the Electron Tube Amplifier". New York: Ziff-Davis. Radio & Television News p. 44 Von Lieben would later make refinements to triode vacuum tubes.