1. What are stack lights?

Stack lights, also name signal tower lights, indicator lights, warning lights, industrial signal lights, tower lights and light towers, are commonly used on equipment in industrial manufacturing and process control environments to provide visual and audible pilot of a machine state or process event to machine operators.

2. How to does stack lights work?

Stack lights are passive devices that may be controlled directly by programmable logic controllers(PLC), distributed control systems, PC control systems or hardwired to machine controls such as timers, sensors and latching relays.

Flashing control may be provided by the stack light's internal circuitry or externally controlled with timers or programmable logic controllers(PLC).

3. What is the meaning of different colors of stack lights?

According to the IEC60073 standard, commonly used colour codes for machine state conditions include:

RED: Failure conditions such as an emergency stop or machine fault

YELLOW: Warnings such as over-temperature or over-pressure conditions

GREEN: Normal machine or process operation

BLUE: External help request, where an operator might be requesting raw materials, scheduling or maintenance personnel assistance

WHITE: User-defined conditions to a specific machine, often related to productivity monitoring

Others, optionally an audible alarm buzzer, typically in the range of 70–120dB, may be added to alert machine operators to high priority conditions.