the Vari-Pac 3-way heat lamp contained two separate filaments in the same bulb
Vari-Pac 3-way heat lamp
The electric circuit of a heat lamp for therapeutic
use did not differ from that of an incandescent lamp
for illumination purposes or that of an electric
heater: An AC- or DC supply voltage, connected to
the two leads of the infrared source directly or
through an on/off switch and/or a safety fuse. Some
Kanthal elements consisted of two or more sections
that could be selected independently or in
combination. In rare occasions, like with the
Vari-Pac heat lamp on display here, an
incandescent lamp with two separate filaments in
the same bulb was operated in the same way. Using
a 3-pole socket and two filaments, one of 100- and
one of 150 Watt, connected in a V-configuration, a
wattage of 100, 150 or (by connecting both
filaments to the supply lead) 250 Watt could be