Fort Smart Outdoor Solar Powered Siren for Smart Home Alarm System. This siren is designed to be mounted on outside walls to sound an alarm at up to 110 decibels. With a wide solar panel and rechargeable backup battery which can last up to 40 hours, the Smart Alarm system will still be active for days in the event of a power cut or if the solar panel is covered. It links with the click of a button to a Smart Alarm Hub via radio frequency and can be placed up to 80m (clear line of site) from the hub.