This is a wireless strobe/siren however it does require to be plugged onto a mains power point. It comes with a 12volt power adaptor. There is a tamper switch on the casing and will trigger the siren and strobe if the front cover is removed or if the casing is removed from the wall. It has a built-in rechargeable battery backup in case of power failure. When your alarm system is in armed mode a red LED will flash slowly to advise you the alarm is turned on.

Specifications:
Transmission range: 40 metres (open area)
Transmission range: 30 metres (through two walls)
Battery Type:  1 x 18650 Rechargeable Lithium
Battery life: 5 years