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ID = 28976
Great Britain (UK)
Brand: Standard Telephones and Cables Ltd. (STC); London, Foots Cray
Developer: Standard Telephones and Cables Ltd. (STC); London, Foots Cray 
Tube type:  Triode, vacuum   Audio Frequency 
  Ca. 1925 up to 1945 rare.
Identical to 4021A = 3A/109A = SY4021A = 4630 = CV1671
Similar Tubes
Heater different:

Base UV-Base (4 Pins+Bayonet, USA 1914 WE)
Was used by Telephony
Filament Vf 4 Volts / If 0.25 Ampere / Direct

Telephone repeater tube designed for DC series or parallel operation.

Dimensions (WHD)
incl. pins / tip
57 x 114 x mm / 2.24 x 4.49 x inch
Weight 65 g / 2.29 oz
Literature Saga of the Vacuum Tube, Tyne   page 369
- - Manufacturers Literature   
4021A: Fin Stewart
Fin Stewart


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