An electrical switch used within an electrical system to control the on/off state of a device. A contactor is generally operated by an electromagnetic coil.
An alarm unit used in cable pressurization schemes which activates when there is a fall in pressure. Also a large mechanical relay used to open or close electrical circuits.
One or more sets of contacts that are opened or closed by a magnetic coil. The contactor is similar to a relay but normally larger. By definition, the contactor is rated for more than 15 A.