Connect your compatible BRK or First Alert alarm to an auxiliary device with the BRK RM4 Smart Relay for First Alert. Using this interconnected smoke detector relay, your BRK or First Alert smoke, heat, or carbon monoxide detector can automatically activate a strobe light, siren, bell, door closer, exhaust fan, or similar auxiliary device when the detector's alarm sounds. The interconnected smoke detector relay is 120-volt AC powered and allows you to create a connected alarm system that enhances the effectiveness of your alarm. Faster turnarounds on job sites with the easy-to-install, most-trusted alarms in home safety