Maker's Name: 
Telegraphie Militaire
Where made: 
circa 1916

First World War era triode valve used in military radio receivers.

The valve has a spherical glass envelope and a 4-pin crucifix base with birfurcated brass pins. The base has a lacquered brass skirt.

The electrodes have a horizontal coaxial structure, with a cylindrical anode enclosing a helical grid and straight tungsten filament.

The filament ran on 4V at 0.75A. The TM was one of the first valves with a hard vacuum.