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US 3,968,395 AGranted
Two filament electric bulb traffic light
AssigneeSiemens Aktiengesellschaft
InventorAnton Obermaier
Life of this patent
Estimating the term…
Abstract
A two filament light bulb in a traffic signal generator has a main filament and an auxiliary filament. The light bulb is a two filament halogen light bulb and the traffic light controller includes apparatus for periodically and alternately exchanging the role of main and auxiliary for the two filaments.
Claims3
A traffic control arrangement for a traffic light, comprising:
- a halogen electric lamp, said halogen electric lamp including two filaments which are subject to the tungsten-halogen cyclic process;
- and control means connected to each of said filaments and operable to periodically and alternately energize said filaments for approximately equal periods of time which are within the interval within which the tungsten halogen process does not become effective, said control means including detecting means connected to said filaments to detect filament failure and means connected to said detecting means and to said filaments for operating the lamp on one filament in response to detection of failure of the other filament.
Dependencies are inferred from the claim text.