The Sylvania 1B59 is a gas-filled glow modulator tube that was used primarily in early fax machines and military imaging devices. Operating on the same principles as a hollow cathode lamp, the 1B59 produces a concentrated blue-orange spot of light that is projected out of the tube's flat front window. When attached to a moving carriage or mounted in front of a rotating mirror, this point of light can be used to draw images on photosensitive paper. The 1B59 has an operating voltage of 140 volts and can be switched on and off at speeds of up to 15kHz. This tube was made in several different variants, with some versions of the tube being packaged in a more traditional rounded T9 octal envelope covered in a black paint overlay. The 1B59 is believed to have been released sometime around 1946.
One noteworthy use of the Sylvania 1B59 was in the imaging equipment on-board the OV-1C Mohawk, a US Army observation aircraft. The OV-1C was equipped with a UAS-4 infrared surveillance system, which used a 1B59 to paint infrared reconnaissance data onto strips of film.
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