The Fire Sentry 0914 smoke alarm is a battery operated smoke alarm that utilizes ionization sensing technology. The four (4) inch unit is smaller in diameter giving it discreet design with the same quality you would expect in a Kidde manufactured product. The 0914 is powered by a 9V battery, providing continuous protection, even during power outages. This easy to install unit includes a test button to verify the detection electronics are working as intended.