IEEE Power & Energy Magazine - January/February 2017 - 83

In 1932, a large installation of this
type was made by Westinghouse to
control the stage lighting in the Center
Theatre (now long gone), which was a
part of the mammoth Rockefeller Center complex being constructed in Manhattan at that time. However, in the
same year, GE installed what would be
their largest thyratron-reactor control
in the world-renowned theater that is
still in operation today, Radio City Music Hall, also in Rockefeller Center.
as in the Earl Carroll Theatre, the
control board for Radio City Music Hall
was installed in a smaller pit outside of
the large orchestra pit. again, of course,
the large racks containing the saturable
core reactors and the control tubes were
located out of the way in the basement.
This control board used a new type of
dimmer controlling device that was referred to as a solenoid potentiometer.
It replaced the simple resistive potentiometers used previously to control the
signal to the grid of the thyratron tube.

This new device consisted of a coil of
wire with a movable iron core inside.
Ironically, this basically is the same configuration used at Daly's Theatre back in
the 1880s, which was a total failure. In
this case, however, the solenoid was not
being used to control the lamps directly.
The solenoid potentiometer concept
was developed by a research engineer
at the schenectady GE plant by the
name of C. (Chauncey) Guy suits, who
was later awarded a patent for its use
in this regard. He eventually became
the director of the famed GE Research
Laboratory following W.D. Coolidge,
the inventor of the X-ray tube.
suits also was instrumental in the development of a saturable core reactor
control scheme used on the nearly 200ft (61-m)-long "General Electric" sign
at the plant in schenectady. He used circuitry of his own invention, which was
capable of creating a timed brightening
and dimming of lamps with no mechanical components. Various portions of the

sign (with a total of 1,400 lamps) were
illuminated in a sequence that was repeated over and over. This sign is still in
place on top of Building 37 of the plant
but no longer exhibits this interesting sequence. It is simply lit up at night.
The Radio City Music Hall installation controlled a total of about 320 dimmers, ranging from 2 to 16 kW capacity
each. sixty or so of these dimmers were
used to control elaborate lighting in the
auditorium (as in the Earl Carroll Theatre) with lighting fixtures colored in
amber, red, green and blue (the additive
mixing of these approximating white
light). The total connected lighting load
was about 3,300 kW, and the board was
arranged for five-scene preset control
(see Figure 7).
Following this, a GE thyratron-reactor
installation was made at the old Metropolitan Opera House located on 39th street
in Manhattan prior to the construction
of Lincoln Center. This controlled 170
dimmers, ranging from 2 to 12 kW each,

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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - January/February 2017