An indicator light is basically an electrical component that indicates when something is happening. It may indicate a fault or run situation. For example an indicator lamp might be wired to the front of an electrical control panel to tell an operator when a motor on a factory floor is turned on. Their operation and construction is very simple, these days they are usually just LEDs encased is some kind of coloured plastic.
Indicators In A Circuit
We can see in the above image of a motor control circuit that the green indicator is wired to indicate when the motor is running and the red light is installed to show when the motor is in fault. While contactor K1 and its auxiliaries are closed, current will flow through the green light. If there was an overcurrent situation through O/L1 then the red fault light would illuminate instead. Indicator lights are made to for many different voltage applications.
To Recap
An indicator light is an electrical component that indicates when something is happening in an electrical circuit, for example when a motor is running or when it is in fault.
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