Interior Lighting for Designers

to strike the arc instantly. This is a violent
action that requires cathodes able to with-
stand the jolt of instant starting.
Because preheating is unnecessary with
instant-start lamps, only one external con-
tact is located on each end of the lamp.
Some instant-start lamps have bipin bases;
lamps with single-pin bases are called
slimlinelamps. In these lamps, the pins are
connected inside the base.
Slimline lamps can be operated at more
than one current and wattage. For this
reason, they are identified by length rather

than lamp wattage. The number following

the “F” in the designation is the nominal

lamp length. For example, F96T12/RE830 is

a 96 in (8 ft), 1½-in-diameter, slimline lamp

with rare-earth phosphors and a correlated

color temperature of 3000 K.

Rapid-startlamps combine the features

of the preheat and instant-start circuits

(figure 7.6). Starters are unnecessary. The

ballasts have separate windings that heat

the cathodes continuously; the lamps start

almost instantly after being switched on, but

less voltage is required for starting than with

Figure 7.6Rapid-start lamp diameters and bases at one-half actual size.