Early radio inventors used a variety of methods to detect radio waves. Those early detectors tended to be slow and cumbersome in operation and that limited transmission speed. In 1906, Lee de Forest built on the work of Thomas Edison and John Ambrose Fleming and invented an electron tube he called an “Audion.” His tube contained three internal elements: a filament, an electrode and a control grid. Today we call tubes of this type “triodes.” In 1907 De Forest received U.S. Patent #841,387 for his invention, one of the most important in the history of radio.
For transatlantic radio experiment. Patent dates: 15 January 1907 (2), 18 February 1908, 27 April 1915. A 4-pin bayonet base with plastic shell. Tipped, T-shaped glass envelope. Bureau of Standards property number: "R-1976". Set in a plastic surface-mounted socket.
Marked: "1701". In original box with instruction sheet. A moderate power triode designed for use as an audio frequency amplifier, but can also be used as an RF amplifier or oscillator. Eff = 4.5 volts; Ip = 1.6 amperes. Ep = 200 - 400 volts; Ip = 8 - 40 milliamps. Mu = 6.7 - 7.4; Rp = 3500 - 4800 ohms. Tyne notes that the locking pin on 205 type tubes was set 45o differently from other tubes to prevent low-power tubes from being inadvertently substituted. Reference: Tyne, "Saga of the Vacuum Tube," page 287.
"The No. 205D is a three-element filamentary type tube intended for use as a radio-frequency amplifier, oscillator, modulator, and audio-frequency amplifier in output stages when moderate powers are required." Reference: Western Electric 205D data sheet: https://www.westernelectric.com/s/205D.pdf.
Western Electric type 216A high-vacuum triode amplifier - oscillator. A 4-pin base with tipped G-shaped envelope. Marked: "Western Electric / Made in U.S.A. / 216 A / Pat. in U.S.A. / 1-15-07 2-18-08 10-17-16 12-19-16 12-17-18 6-24-19 1-27-20 6-13-22 / Pats Applied for"; paper label around neck reads: "Licensed for use only as part of the Western Electric Loud Speaking Telephone Outfit." Reference: https://www.westernelectric.com/s/216A.pdf; Tyne, "Saga of the Vacuum tube," pages 291-293.
5 watt transmitting triode. A 4-pin plastic base with S-shaped glass envelope, getter stain. Stamped on base: "de Forest / Audion / 510"; inked on stem assembly: "4753 3K23". Reference: https://www.radiomuseum.org/tubes/tube_510.html. Object is on the right in the photo.
Seven pins surrounding an exhaust tip on the bottom. T-shaped envelope with glass seam around the base. Stamped: "826 [twice] / SC961A / Ken-Rad / Made in U.S.A." Reference: https://www.radiomuseum.org/tubes/tube_826.html.
VT-2 tube with envelope. Audion is being used generically here. Brass 4-pin base (gold tips on tines) with bakelite insulator, two plates and grids with one emitter. Stamped on the shell: "Pat. in U.S.A. / 1-15-07 Two patents / 2-18-03 4-27-15 / 12-19-16 / Pat. Applied For". Reference: Tyne, "Saga of the Vacuum Tube" 100-103, 286-287; https://www.radiomuseum.org/tubes/tube_vt2.html.
Marked: "1701". In original box with instruction sheet. A moderate power triode designed for use as an audio frequency amplifier, but can also be used as an RF amplifier or oscillator. Eff = 4.5 volts; Ip = 1.6 amperes. Ep = 200 - 400 volts; Ip = 8 - 40 milliamps. Mu = 6.7 - 7.4; Rp = 3500 - 4800 ohms. Tyne notes that the locking pin on 205 type tubes was set 45o differently from other tubes to prevent low-power tubes from being inadvertently substituted. Reference: Tyne, "Saga of the Vacuum Tube," page 287.
"The No. 205D is a three-element filamentary type tube intended for use as a radio-frequency amplifier, oscillator, modulator, and audio-frequency amplifier in output stages when moderate powers are required." Reference: Western Electric 205D data sheet: https://www.westernelectric.com/s/205D.pdf.
VT-2 tube with envelope. Audion is being used generically here. "C286" on box. Brass 4-pin base (gold tips on tines) with bakelite insulator, two plates and grids with one emitter. Tipped G-shaped envelope. Stamped: "49399" on the envelope; on the shell: "Pat. in U.S.A. / 1-15-07 Two patents / 2-18-03 4-27-15 / 12-19-16 / Pat. Applied For". Reference: Tyne, "Saga of the Vacuum Tube" 100-103, 286-287; https://www.radiomuseum.org/tubes/tube_vt2.html.