Between the world wars, designers of
lighting control
systems concentrated on improving the control board, or control desk as it was then called. In 1925 the Royal College of Music in London installed a new system of 32 dimmers, which used hydraulic pressure to move the levers of the dimmers. In 1929, Moss Munsell, one of the founders of "Strand Electric", took out a patent on an electromagnetic clutch designed to move dimmer levers.
In 1935 Fred Bentham, a pioneer of modern lighting in England, developed a control system known as the
Light
Console, with the help of an organ manufacturer. The light
console
used a system of organ keys and pedals to control the connection of dimmer levels to various motors, thus creating groups of dimmers which moved in unison. The keys were operated by pressure: light pressure increased the light, and strong pressure decreased it, while foot pedals controlled the timing of the lighting changes. This innovative board could be located in a special
lighting booth
at the rear of the hall, facing the stage. The operator, seated at the board, could now see everything happening on the stage, and adjust the light accordingly.
In 1930 Professor Stanley McCandless designed a new control board, which was built for the Cleveland Severance Hall by Westinghouse. The board was equipped with a
master
control and with pedals which controlled the timing of the lighting changes, and lighting states could be prepared in advance (preset).
A further development in variable transformers came with the introduction of saturable reactor dimmers, which used a low-voltage DC current produced by a
potentiometer
in order to change the magnetic
impedance
of the transformer, and thus the electric
voltage
produced. This made it possible to do away with the mechanical
tracker wire
systems, replacing them with
remote control
wires.
In the late 40's the first
electronic dimmer
appeared. George C. Izenour, a lecturer in theatre lighting at Yale university, installed electronic dimmers at his university theatre in 1947. These dimmers used Thyratron tubes as a
voltage
switching device and were efficient enough, yet they were not widely used, owing to their high cost and complex installation. Ten years later a more sophisticated form of control system appeared, based on a new invention - the transistor. In 1959 the
thyristor
voltage switching device was developed - a transistor-like component also known as the silicon controlled rectifier -
SCR
for short. The development of electronic dimmers initiated a revolution in lighting control.
