Summary

Low mu triode intended for use in telephone repeater applications. Manufacturer: Standard Telephones & Cables, Sydney, Australia.
The SY4101D was the STC (Australia) version of the Western Electric 101D. The letters SY indicate Sydney and the 4 prefix indicates STC manufacture. The 101D was introduced by Western Electric at the end of 1921 and remained in production, with a number of upgrades, until the 1950s.
1 amp directly heated cathode designed to be used in a controlled current environment.
The STC 4101D was superseded by the 3A/141A in 1946.

Physical Description

Spherical glass bulb with top exhaust tip and 4 pin UV style Bakelite base

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