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ID = 19708
Great Britain (UK)
Brand: Marconi-Osram - (Valves/Tubes); GB
Developer: Marconi's Wireless Telegraph Co. Ltd. 
Tube type:  Transmitting Triode, air cooled   Power/Output 
  <1925 very rare. ***
Identical to MT1_MOV = MT1_Ediswan
Similar Tubes
Heater different:
First year Mar.1919 ?? British Radio Valves - The Vintage Years: 1904-1925 page 129 (before = Ediswan)
First Source (s)
Mar.1919 : British Radio Valves - The Vintage Years: 1904-1925 p.127

Base Wires
Was used by Transmittertube (Radio)
Filament Vf 9 Volts / If 5.5 Ampere / Direct / Specified voltage AC/DC

Ediswan is probably producing until 1919 when production went to Osram. Fin Stewart lists MT1, MT3, MT4 and MT5 being produced by Osram (in "History of GEC and the Marconi Osram Valve", page 77.) First made by Osram lamp Works March 1919, before the MOV agreement was signed - 26/11/1919. Tube shown as made by MOV in the "Exhibit of Wireless Valves at the Exhibition of the Physical Society January 1920", page 12.

Tyne and Thrower assign it to MOV.

Similar to T-250, but for a lower filament voltage. The two tubes were interchangeable with each other, properly adjusting the voltage drop variable resistor used in series to the filament of each tube, as clearly shown in the application diagram below.

By the way, it was common practice to etch the exact voltage value on the glass of each transmitting tube with tungsten filament, individually adjusting the series resistor. (Ref. 'Thermoionic Tubes' by John Scott-Taggart, 1921)

Text in other languages (may differ)
Dimensions (WHD)
incl. pins / tip
215 x 120 x mm / 8.46 x 4.72 x inch
Tube prices 1 Tube prices (visible for members only)
Information source Saga of the Vacuum Tube, Tyne   p.381
- - Manufacturers Literature   

MT1_MOV: Ali e Onde, Franco Soresini
Emilio Ciardiello

MT1_MOV: Banneitz, TB der drahtl. Teleph. 1927
Anonymous 15 Collector

Usage in Models 1= 1925 ; 1= 1927?

Quantity of Models at with this tube (valve, valves, valvola, valvole, válvula, lampe):2


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