Universal Security Instruments USI-1204 University Security Instruments Electric 1204 Hardwired Ionization Smoke & Fire Alarm | 120-Volt Fast Responding Alarm - Comes with Backup Battery QUICK RESPONSE | Ionization Smoke and Fire Alarm Responds Quickly to Fast-Flaming Fires to Protect your Family against Deadly Threats in the Home EASY READ | Red LED Light Flashes when Smoke is Detected and the Green LED Light Indicates that Power is Functioning 120-VOLT | AC Hardwired Alarm with Backup Battery is Suitable for Houses, Apartments and Mobile Homes FEATURES | Convenient Silencer Button for Non-Hazardous Alarms - Smart Interconnect to Connect up to 18 Units