Summary

Power triode used in telephone repeater systems.
SY in the type number indicated that this valve was made in the Sydney factory of STC, the first 4 indicates that it is the STC version of the 104D.
Equivalent to the Western Electric 104D. 1 amp directly heated cathode.
Manufacturer: Standard Telephones and Cables, Alexandria, NSW.

Physical Description

Spherical bulb with exhaust tip on top with brown bakelite four pin UV style base

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