All the same features and quality as the other Gentex smoke alarm models, with the addition of battery backup. Battery backup operates audible alarm only. This is a photoelectric single station smoke alarm designed to give reliable early warning of the presence of smoke where both audible and visual alarms are required. One year warranty. The smoke alarm operates on the light scattering principle, a superior method of detection in smoldering fires. It has a pulsing LED light source and a photodiode sensor in a fully screened sensing chamber. When smoke enters the chamber, the infrared beam is deflected onto the sensor. The LED rate increases to 8 times the normal pulse rate, and after the photodiode confirms the presence of smoke for 2 consecutive pulses, it will produce the signal necessary to trip the audible and strobe light alarms. Features: 177 candela rating (very bright strobe light) Solid state 90dB horn (very loud) Full function test switch (easy for you to test that it is working) Flashes 60 times per minute Meets state, federal, and ADA requirements Mounting hardware 9V battery backup (audible alarm only) UL Listed (USA) Click for user manual Options available: Ceiling Mount This model is hard-wired so you would need an electrician to hook it up Quick-disconnect wiring harness Tandem connection up to 6 detectors per system Wall Mount Electrician is not required for installation 9 foot line cord