Switches are marked with different labels to identify ratings, types, and acceptable wire types. The UL label will also tell you if the device has been tested for safety by an indepent testing agency, such as the Underwriters Laboratories. A switch will tell you if it's approved for alternating current (AC) applications only, the voltage rating, and the maximum allowable amperage.
The labels will tell you what the allowable wire connections are for the switch. If it reads, "use CU wire only", only copper wire may be used for the connections, not aluminum. If it says, "CO/ALR", that means that either copper or aluminum wire installation is allowable. The manufacturer lists these labels to identify all of the previously mentioned labels. This will ensure proper installation of switches in your home.
