The System Sensor EOLR-1 is an epoxy encased, single-pole relay designed to supervise power supplies for fire protection systems. 4-wire smoke and heat detectors draw power from an auxiliary power supply. The EOLR-1 offers a way for your alarm control panel to be notified if power to your smoke/heat detectors is lost for any reason. This relay should be wired in series at the end of line (EOL) at the last smoke/heat in the series loop. Then if any wiring issue, or power problem prevents power from reaching any of the smokes the relay will throw and put the fire zone into trouble on the system.
Depending on how the zone is configured it can trigger local audible alerts on the keypads and/or sirens, remote phone calls from your central station and/or text/email notifications from interactive services like Total Connect 2.0 or Alarm.com. Traditionally, as this device is wired into the fire zone, when the relay trips, upon power loss, it opens the fire zone and causes a trouble response. This will locally trigger sound from the keypads until a disarm is entered to clear the trouble. You can setup phone calls from the central station if you are monitored as well.
Generally, fire detection systems are configured to have wiring supervision on the data wires back to the control panel through the use of an end of line resistor (EOLR). If a data wire is cut or somehow loses its connection back to the system there is a notification. For 2-wire devices that draw power and send data on the same wires that is really all you need to truly supervise all aspects of the unit. 4-Wire smokes behave differently. Because they are Normally Open devices, when they lose power, they do not change state. Therefore, without the EOLR-1, it would be possible to lose power to the 4-wire smoke detectors, and never know it, until tragedy strikes. In other words, the EOLR-1 is required for global supervision of your 4-Wire fire protection system.