Which safety measure is critical when working on live circuits?

When working on live circuits, disconnecting power from the circuit is the critical safety measure. This action completely eliminates the risk of electric shock and ensures that no current is flowing through the wires while you are working on them. It is the safest approach to electrical work because it allows technicians to perform tasks without the hazard of being electrocuted.

While wearing rubber-soled shoes can provide some insulation and reduce the risk of shock when working near live circuits, it does not eliminate the hazard if the circuit remains powered. Working alone is generally discouraged for safety reasons, as having a partner can provide assistance in an emergency. Using only one hand while making connections is a method to reduce shock risks by minimizing the path to ground through the body; however, this still does not negate the danger of working on a live circuit. Taking the step to disconnect power is the most effective and responsible safety measure in this context.