A pilot device is the term given to any two-wire control circuit component that mechanically closes and opens its control contacts, depending on the state of the medium it is measuring.

Pilot Device

A manual or automatic device used to initiate control operations, such as signaling or actuating other devices within an electrical system.

Two-wire Control

Two-wire control is a simple control circuit configuration where the device is controlled directly by a switch or relay in one of the two wires supplying power.

Control Contacts

Control contacts are the parts of a relay or switch that make or break the connection in a control circuit, influencing the operation of a system or device.