No confusion here - this unit has a voice alarm that announces "Fire! Fire!" in addition to a loud, 85dB beeping when smoke or fire is detected. Sealed-in lithium battery lasts the entire ten-year lifespan of the alarm. It's quick and easy to install; alarm automatically activates when attached to the mounting bracket. Smoke alarm contains photoelectric sensor that may detect visible particles associated with smoldering fires sooner than ionization alarms. Includes a test/hush button that tests alarm circuitry and temporarily silences nuisance alarms. Rapidly flashing LED lights alert users if alarm has sounded since the last time the test/reset button was used.