120V Talking Smoke/Carbon Monoxide Combo AC combination alarm protects from both smoke/fire and carbon monoxide Ionization smoke/fire alarm and electrochemical CO alarm Loud voice alarm indicator announces: "Fire! Fire!" or "Warning! Carbon Monoxide!" Back up battery included These are good until 2027. I purchased, installed and removed due to renovation. They are in excellent like new working condition. These retail for $65.00 each new. Asking $20.00 each or $65.00 for the lot of 4 Also have 6 Kidde Photoelectric Smoke Detector(see my other add)