A24V 5A polarised relay designed for use in 24V fire alarm systems. Includes a keyswitch isolation facility allowing the relay operation to be temporarily disabled during routine test and maintenanceto prevent autodiallers, water sprinklers, rollershutters, etc., from activating. When isolated, theunits Isolated LED will flash and a warning beeper will sound every 8seconds to ensure devices are not inadvertently left in the isolated state. Relay is triggerable via a control panels open collector output or a standard polarised fire alarm sounder circuit (if connecting to a sounder circuit, the relay will return to its normal state when the fire condition is cleared or silenced check with the approving authority that this arrangement is acceptable prior to installation). Fits on standard UK 25mm flush or surface mount back boxes.