What is the function of the "CO/ALR" marking on devices?

The "CO/ALR" marking on electrical devices signifies that the device is suitable for use with both aluminum and copper conductors. This is particularly important because aluminum and copper have different physical and thermal properties, which can affect how well electrical connections function. The CO/ALR marking assures installers that the device has been tested and certified to handle the unique characteristics of both types of conductors, minimizing the risk of overheating or connection failure when used with either material.

Understanding this marking is crucial for electricians and installers to ensure safety and reliability in residential and commercial installations. It allows for flexibility in choosing materials based on availability and cost without compromising safety standards. Other options do not correctly represent this compatibility, either limiting usage to a single conductor type or suggesting a more general safety compliance that does not pertain to specific material suitability.