Smoke Detector, Hardwired Interconnected Smoke Detectors, Smoke Alarm With Product Details [Hardwired interconnection] Up to 12 smoke alarms can be interconnected to cover your entire home. When one detects smoke, they all make a sound to alert everyone in the house, creating an interconnected safety net for your home. [9V Battery backup] Hardwired smoke detectors are equipped with DC 9V batteries. Ensure that all units are always connected and continue to function properly, even in the event of a power failure. Low battery alarm reminds you to replace the battery as soon as possible. If an error occurs, the system automatically triggers the fault mode, prompting you to check the device. [Test Mute button and LED light] It is connected with other alarms. Just press the test/mute button on one of the units to test or mute the entire interconnected system. If the smoke alarm is in normal working condition, the green LED light is always on and the red LED light flashes every 32 seconds [Photoelectric smoke sensor] Based on advanced photoelectric technology, smoke alarms can be more sensitive, fast, accurate measurement of smoke levels. More than 85 decibels of alarm sound, you can more clearly hear the danger coming. [Simple installation] The installation of smoke alarm is very simple. The AC connector is connected only to the mains power and signal cables. (Please connect as instructed) Payment We accept PayPal and credit cards via PayPal. Taxes - US We collect sales tax, as required by law. Shipping We make every effort of shipping within 3 business day of payment clearing. The estimated delivery time is 2 - 5 business days from the shipping date. Policies If you do need to return your item, please contact us via email (you will receive an email when your product ships with additional details - Subject: Important information about your purchase). You will then be provided with a return shipping label and packing slip. Pack the item carefully. Include the packing slip, apply the shipping label, and return the item within 30 business days of the date you request a return, or your return will be canceled. Once we receive your order we will inspect the return. Please allow up to 5 business days of receiving the returned item for your refund.