ADVANCED PHOTOELECTRIC SENSORS: Smoke detector equipped with photoelectric sensors have an average response time of 15-50 minutes faster than ionisation sensors. An audible alarm of ＞85dB at 3 metres helps you to prevent fires in their early stages..MINI BUT MIGHTY: Mini smoke detector that can be held with just one hand, is easier to install and disassemble. Equipped with a 10-year long-lasting chip, smoke alarm FJ138 provides long-lasting protection for you and your family..BATTERY EQUIPPED AND REPLACEABLE: There is no need to purchase additional batteries, the battery operated smoke detector FJ138 has already equipped for you! When the battery runs out, simply replace it with a new one to bring your smoke alarm back to life..LOW BATTERY WARNING: When the battery is depleted, the red LED light and chirp will alert you every 32 seconds to replace the battery with a brand new one in time. Please refer to the instruction manual for available battery models and installation instructions..CHOOSE YOUR PREFERRED INSTALLATION METHOD: Fire alarms smoke detectors FJ138 come with screw packs and magnet sheets, which eliminates the need for hard wiring, and you can install it with whichever accessories you want according to the location of the installation..TEST/SILENCE FUNCTION: After confirming that there is no fire hazard, press the silence button for 5 seconds to stop annoying false alarms. Test smoke alarms weekly for normal use.