Simple wire free installation and setup Supplied with required rechargeable batteries that easily charge using the indoor unit and USB charging lead LED indicators for low battery warning and battery charging status Up to 500m transmission range Optional: Connect the outdoor unit to an electronic door lock, utilising the door release button on the indoor unit. NOTE: to power an electronic door lock the outdoor unit requires mains power (not supplied) 12V adaptor 350.006UK, Manufacturer: Mercury