Controlling Light Intensity

To control the intensity of light you need to control the flow of electricity that causes the light bulb filament to glow. You can do that in one of two ways:

Change the amount of voltage that reaches the lamp or bulb
Control the amount of time that electric current flows to the lamp

The first method - controlling voltage - was used by early dimmers. These devices were called rheostats and autotransformers. Both of these converted the unwanted electricity into heat. They were highly inefficient.

In 1961, Joel Spira invented the first electronic dimmer switch. This device controlled the amount of time that current flowed to the lamp or the light bulb. The end result was the same with respect to light intensity but there was very little waste of energy. You see, the electricity never flowed past the switch in the first place. The electronic dimmers cycle on and off so rapidly that our eyeballs and brains can't even tell the electricity was shut off in the first place. After all, imagine having a light bulb on full blast for an hour. It produces, in that time span, a given amount of light. If you were able to rapidly turn on and off the light bulb so that is was actually only on for 30 minutes of the hour, you would use half the electricity, right? That is what new dimmers do. They just do it so well you can't tell they are turning on and off!

With the proper lighting control system, lighting within a room or even throughout and entire home can be controlled automatically when a single lighting control button is pressed, when a button is pressed on a remote control, when a door is opened or even when the sun rises and sets each day.