Glossary of lamps terms
Here is a ready reference of terms for lamps with particular emphasis to railroad applications:
Candela - The candela is a unit of luminous intensity; that is, power emitted by a light source in a particular direction. A candle emits light with a luminous intensity of roughly one candela. FRA requirement is for 200, 000 candelas for headlights, auxiliary or ditch lights.
Conspicuity - The state of being conspicuous. The FRA in their rule refers to conspicuity of headlights, auxiliary and ditch lights for trains so they are conspicuous in their presence to other trains and the public. Motorists and pedestrians become aware of approaching trains at road crossings or pedestrian crossings by seeing the headights. The safe operation of trains is paramount to adequate and reliable illumination of trains.
Dimming resistors - The devices that dim the illumination of headlights. On most trains there is a headlight control switch that has dim, medium and full headlight positions. The headlight control switch selects the appropriate resistor for the level of illumination as desired by the operator. Older locomotives that have 30 volt headlamps have additional resistors to reduce the lamp voltage from the typical 75 volt source.
Diesel Electric locomotive - a locomotive that uses a diesel engine that operates a large generator that produces power to operate the traction motors.
Ditch light or auxiliary lights - Ditch lights and auxiliary lights are used to help illuminate the track for train crews and for the conspicuity of a train to other trains or the public.
Electric locomotive - a locomotive or commuter transit car that uses electricity for propulsion.
Fixture - The device that houses the headlights, auxiliary lights or ditch lights. The fixture clamps the lamp securely in place and has a rubber ring that seals moisture from entering the fixture.
Headlight - Transportation equipment must have adequate illumination for operating crews to see the track ahead and for the travelling public (either pedestrians or motorists) to see the approaching train.
PAR56 - The type and size of a sealed beam lamp. PAR stands for Parabolic Aluminized Reflector. The number 56 is the diameter size in 8th of an inch. PAR56 lamps are 56 eights or 7 inches in diameter. Amglo lamps are stamped in the factory with the lamp voltage, wattage, manufacturer name (A/K), a date code (example B6 means February 2006) and proudly - the "MADE IN USA" stamp.
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