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Demonstration Triode


A cylindrical glass bulb with a metal assembly visible inside standing vertically on a wooden base with six metal terminals aligned on the bottom side. The first two terminals are labeled “PLATE +350v-“. The second (middle) two terminals are labeled “GRID +260v-“. the last two terminals are labeled “FILAMENT 6VOLTS”. On the top right corner of the wooden base is switch level. To the left of the switch is a knob with a needle point which touches circular metal coils. To the left of the knob is a wooden block that supports what looks like an elongated light bulb with a black plastic base, a cylindrical body and . Inside the bulb are various metal components, consisting of metal plate oriented vertically, a metal grid alongside it, and a series of thin metal wires running vertically from the top to the bottom of the bulb.

Accession Number:

Alternative Name:

Primary Materials:

Metal: Copper Alloy; Metal: Iron Alloy; Wood, Glass, Ceramic


Typed on paper stickers affixed between pairs of the electrical terminals: “PLATE +350V” “GRID +250V. -” “FILAMENT 6 VOLTS”

On a sticker affixed to the base of the bulb: “Westinghouse
TYPE W[???-787”

Dimensions (cm):

Height = 27, Length = 20.5, Width = 13.5


The triode tube was developed by Westinghouse as an oversize demonstration tool for teaching in order to explain the features and functions of a triode tube. The switch, terminals and resistor are present to supply and modify power running to the triode tube.


Good: The wooden base is in good condition, although in places the varnish has chipped off at the corners. The metal components such as the switch and resistor are oxidized and dulled, but not corroded. The bulb appears to be in very good condition, with the glass and internal components intact. There appears to be some dark residue (either applied or the dark surface has come off) on the vertical wires that run through the length of the tube.

Associated Instruments:


Triode: Westinghouse; Resistor: The Dayton Fan and Motor Company; Base: Locally made

Date of Manufacture: Early 1930s-1950s


University of Toronto Department of Physics

Additional Information and References:

More information about this triode can be found at Lamps et

Historical Notes: