What safety measure should be taken before working on electrical systems?

The selection of disconnecting the power supply or removing the battery cables before working on electrical systems is essential for ensuring safety. This precaution helps to prevent accidental electrical shocks and potential short circuits that could occur while performing maintenance or repairs.

By disconnecting the power, you effectively eliminate the risk of electrical current flowing through the system while you are working on it. This measure is vital, especially in environments where water is present, as water is a good conductor of electricity and increases the risk of electric shock.

In contrast, having electrical devices plugged in or turning on devices for testing can create hazardous conditions, where live circuits could lead to accidents. Simply wearing insulating gloves does not provide adequate protection if the system remains energized; thus, turning off the power supply is the fundamental first step to ensuring a safe working environment.