How do I replace batteries in wireless sensors, and how long do they last?

Use only batteries recommended by your installer as replacements. Each wireless sensor uses either a 9-volt or 3-volt battery; alkaline batteries provide a minimum of 1 year of operation and typically 2–4 years, while 3-volt lithium batteries can last 4 or more years. After replacing the battery, activate the sensor (open/close the door or window) to send a 'good battery' signal to the control, which will clear the low battery display. If the sensor is not activated, the display will automatically clear within approximately 1 hour. (Page 40)