Chap.4 Part 2

A relay that activates an alarm or signal

A relay that operates in order to assist another relay or device in the performance of its function

A relay that operates when the magnitude of one electrical quantity exceeds the magnitude of a similar electrical quantity by a predetermined value

A relay that renders some other relay or device inoperative, when a predetermined condition is reached

A form of pilot protection in which high-frequency
current is transmitted over a metallic circuit (usually the line being protected) in order to
communicate between circuit terminals

A form of auxiliary relay, used with an electrically operated device, to control the closing of the device operating circuit. This eliminates the need for the main operating current to pass through the control switch or other initiating device.