What essential device must all battery powered equipment be equipped with?

All battery-powered equipment must be equipped with an under voltage indicator because this device plays a crucial role in maintaining operational safety. The under voltage indicator alerts users when the voltage in the battery system falls below a certain level, which can help prevent equipment failure or damage due to insufficient power. It is essential for ensuring that equipment operates within its safe voltage range, thereby protecting both the equipment and the operator.

In mining, where equipment reliability is critical and safety hazards are prevalent, this indicator is particularly important. It enables early detection of potential battery issues, allowing for timely maintenance and preventing hazardous scenarios that could arise from using equipment with failing batteries.

The other options, while related to safety, do not specifically address the unique challenges posed by battery-powered equipment. For instance, locking mechanisms and safety switches are more relevant to mechanical and electrical safety in preventing accidental activation, whereas a fault current interrupter focuses on circuit integrity and electrical faults rather than directly monitoring battery performance.