1. Install the battery: Outdoor- is power supplied by 4pcs alkaline battery, easy to replace the battery, indoor- is power supplied by rechargeable - battery. 2. Long standby time: long standby time for outdoor- up to six months 3. Big and adjustable speaker, clear voice, can be used as mobile . 1. Long wireless distance up to 200M 2. installed with tape 3. Outdoor- pair with indoor- by learning code, 1 outdoor- can paired with N indoor- and no interference each other. Power mode: AAA dry battery Power supply voltage: 5 (V) Type: wireless door size:100*60*14.8mm Material:ABS colour:gray Package Contents: 2 * Intercom doorbell(1 outdoor- and 1indoor-) 1 * USB Charging Cable Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.