What types of devices monitor mechanical switches in traffic signal controller cabinets?

The correct choice is related to the function and purpose of isolators within traffic signal controller cabinets. Isolators are devices that provide electrical isolation and protection, ensuring that any faults or abnormal conditions do not affect the overall traffic signal system. They help in monitoring the status of mechanical switches by preventing interference and allowing the system to operate safely and reliably.

Isolators are typically used to keep the control circuits separate from the main power circuits, which is crucial in maintaining the integrity of the signal operations. They help in detecting if switches are functioning correctly and prevent possible short circuits or feedback issues that could arise from mechanical failures.

In contrast, capacitors store electrical energy, relays act as switches to control circuits, and conductors are materials through which electricity flows. While these devices play important roles in electrical and electronic systems, they do not specifically monitor mechanical switches in the context of traffic signal controllers like isolators do.