A pushbutton is a simple switch mechanism for controlling some aspect of a machine or a process. Pushbuttons are often color coded to associate them with their function so that the operator will not push the wrong button in error. Common colors are red for stopping and green for starting the machine or process. Maintained and spring return (momentary) operators as well as illuminated and non-illuminated versions are offered.
A pilot light provides indication of machine function and status. Incandescent or LED lamps are commonly used for illumination. Common colors are red for stop, green for start or on, and yellow for caution.
Industrial versions are designed to be water- and oil-tight to withstand the factory-floor environment. 16mm, 22mm, and 30.5mm mounting-hole sizes are most common.