Handy Little Relay 24VDC - 

The polarised version of the Handy Little Relay 24V module is a simple-to-fit unit for use wherever dry contact, voltage-free switching is required or where there is a need for higher than usual currents and voltages to be switched. Its compact size makes it easy to fit inside the majority of control panels. The polarised function enables it to be used in fire alarm and similar systems, where the polarity of the output to bells, sounders etc is reversed when in ‘alarm' mode. Common applications include switching extra sounders and emergency door openings in fire alarm systems.