A stylish and attractive wireless digital intercom that allows you to talk to your visitors before opening the door. No wires are required between the outdoor and indoor units, making this system very simple to install. Both units are powered by a rechargeable battery with the indoor unit doubling as a battery charger when connected to a suitable USB power source using the charging lead provided. Its also possible to 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 using the additional 12V adaptor 350.006UK (not supplied) Ideal for use in domestic and business applications and helpful for the elderly or less mobile.Frequency: 426~440 MHzvbCrLfTransmission distance: Up to 500m (open area)vbCrLfPower supply : indoor unit: 18650 Lithium rechargeable battery (DC3.7V)vbCrLfPower supply : outdoor unit: 18650 Lithium rechargeable battery (DC3.7V) or DC12V 1~2A Mains adaptor (not supplied)vbCrLfDimensions (indoor unit): 154 x 54 x 36mmvbCrLfDimensions (outdoor unit): 158 x 62 x 50.5mmvbCrLfIP rating: IP44 (outdoor unit only)vbCrLfWeight (indoor unit): 165g (including battery)vbCrLfWeight (outdoor unit): 220g (including cover & battery)