Which components are typically not used to prevent entry into a machine during operation?

Regulators and valves are primarily components related to controlling the flow and pressure of fluids within a system rather than preventing entry into a machine during operation. They play a crucial role in fluid dynamics and process control but do not serve as safety devices to restrict access to moving parts or hazardous areas of machinery.

On the other hand, magnetic sensors, capacitive sensors, limit switches, photocells, guards, and light curtains are specifically designed to enhance safety by creating a barrier or an alert system that prevents accidental access to machinery while in operation. These safety mechanisms function to ensure that personnel cannot inadvertently come into contact with dangerous machine elements, thereby reducing the risk of injury.