No installation required, can be placed anywhere. test button. Silence button for unwanted alarm & for low battery warning signal. Low battery warning signal. Easy battery replacement (compartment on the front). User-friendly action chart detailing what to do in case of alarm. Led for power, service & alarm. Easy to install with 2xaa battery (with a minimum of 1 year life) & fittings included. Loud 85 decibel alarm.