This signal features an AC type-SA mechanism. A lamp-out relay and transformers are also inside. The hoods are missing.
Signal Indications:
Red - Stop
Red over Yellow - Proceed at slow speed prepared to stop short of another train which is occupying this track.
Yellow - Proceed at slow speed prepared to stop, track unoccupied
Green - Proceed, track unoccupied, next signal clear
(Railway Age - June 28, 1930)
