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CHAPTER XII
Carbon Arc Spot and Flood Lamps, Stereopticon and Effect Machines
THREE types of carbon arc spot and flood lamps are on the market. These are the low intensity A.C., low intensity D.C. and high intensity D.C. types. In the low intensity lamps, both A.C. and D.C, the upper and lower carbons are mounted in line with each other and inclined several degrees from the vertical, as illustrated in Figure 22, page 28. The carbons are usually controlled by hand feed.
In the high intensity, D.C. spot and flood lamp the positive carbon is held in a horizontal position with the negative inclined at sharp angle, as in the high intensity projection lamp, Figure 50, page 60. The carbon feed mechanism is usually motor driven with automatic control.
Stereopticon and effect machines in common use are of two types, the low intensity, D.C. carbon arc and the high intensity, D.C. carbon arc. Both types use the ' 'inclined vertical' ' trim illustrated in Figure 22 and are usually equipped with automatic, motor driven, carbon feed mechanism. An appreciably whiter light is obtained from the high intensity carbon trim than that produced by the low intensity type.
The direct current, low intensity reflecting arc principal is used in the dissolving slide projector. In this lamp the carbon trim is horizontal, as in Figure 35, page 40, and the carbon feed automatic, with motor drive.
The types of carbons used in the foregoing lamps are the same as those used in corresponding types of projection lamps and the instructions given in preceding chapters for the care and operation of the several types of arcs apply, as well, to the lamps here described. Carbon trims and recommended ranges of current are given in Table XII.
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