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The switches are then connected to each other by a pair of wires called "travelers" (or "strappers" in the UK), and the lamp is connected to the common terminal of the second switch, as shown. Using the traveler system, there are four possible permutations of switch positions: two with the light on and two with the light off.
Figure 1 shows a typical relay logic diagram. In this circuit, a STOP/START station is used to control two pilot lights. When the START button is pressed, the control relay energizes and its associated contacts change state. The green pilot light is now ON and the red lamp is OFF.
Two light switches in one box. The switch on the right is a dimmer switch. The switch box is covered by a decorative plate. The first light switch employing "quick-break technology" was invented by John Henry Holmes in 1884 in the Shieldfield district of Newcastle upon Tyne. [1]
Consoles vary in size and complexity, from small preset boards to dedicated moving light consoles. The purpose of all lighting consoles, however is the same: to consolidate control of the lights into an organized, easy-to-use system, so that the lighting designer can concentrate on producing a good show.
Including two for the coil, such a relay has a total of six terminals. The poles may be Form A or Form B (or one of each; the designations NO and NC should be used to resolve the ambiguity). DPDT – Double-Pole Double-Throw relays have two sets of Form C contacts. These are equivalent to two SPDT switches or relays actuated by a single coil.
They enable computer control via networked switches, but do not require it. Their cost is about the same as the older "dimmability" circuitry that they replace in LED bulbs, fixtures or drivers. A residential-type dimmer switch with sliding knob to change brightness. The device is small enough to fit into a regular wall box provided for a switch.
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Two-way: A simple on-off switch: The two terminals are either connected together or disconnected from each other. An example is a light switch. SPST-NO. Form A [4] Single pole, single throw, normally open A simple on-off switch. The two terminals are normally disconnected (open) and are closed when the switch is activated. An example is a ...