Kidde i9030 FyreWatch Battery-Operated Smoke Alarm Test button checks horn, battery and alarm circuitry Low battery indicator warns when battery needs replacement Tamper resist locking pin  helps deter theft or tampering Battery operated, 9 Volt battery included (best with Polaroid 9 Volt batteries) Kiddes smoke alarms meet the requirements of Underwriters Laboratories (UL), an independent facility that tests products for compliance with widely-accepted safety standards