Halogen bulbs are incandescent bulbs. Halogen bulbs, however, are filled with a special gas that actually rebuilds the filament and provides longer average lifespan than normal incandescent bulbs. They come in different shapes and sizes for various different uses. The PAR series of halogen bulbs are flood shaped with heavy, thick glass that is common in many medium to large sized halogen bulbs. PAR stands for parabolic aluminized reflector. These types of bulbs will provide you with a higher light output, a more white-colored light (a higher color temperature - approximately 3000K), and longer life than normal R or BR reflectors.
The PAR46 bulbs are specialized bulbs that are not used in common applications. You can tell what kind of PAR lamp you have by measuring the distance across the widest point of the bulb. The number after 'PAR' shows the number of eighths of an inch in diameter the bulb is. Therefore, PAR46 lamps are 5 3/4 inches across. This type of PAR lamp is referred to as 'sealed beam'.
Sylvania and GE offer PAR46 lamps. They have three kinds of bases; all of which are uncommon bases: Medium Side Prong, Three Prong or 3 Prong, and Screw Terminal. This type of bulb can be used indoors or outdoors. They can be directly exposed to rain or snow and still function normally. They do not need to be covered by a light fixture, which helps make the PAR46 lamps useful in unique situations.
You can get the bulb in several beam spreads. Some are labeled as follows: 3NSP (narrow spot) and 3MFL (medium flood). Others are labeled by the use they generally serve. You can find PAR46 bulbs labeled as Train Warning Light, Mine Locomotive Head, Airplane Halogen, and Traffic Signal. Of course, these bulbs would work in any fixture that had the correct socket, voltage, and wattage maximums, not just locomotives and airplanes.
PAR46 bulbs are available in different wattage and voltage combinations. You can find them in 21 watts all the way up to 450 watts. Voltages range from 5.7 to line voltage. 28 volt, 38 volt, 12 volt, 120 volt, and 13 volt seem to be the most common.
As was made obvious in paragraphs above, people use PAR46 lamps in some unique situations. Due to their large size, uncommon bases, and distinct voltage offerings, the bulbs are not typical in your local lighting shop. Since they are halogen, however, the items shown under this light will appear more brilliant and will display a brilliant color than under normal incandescent bulbs.