Smart Wireless Voice Intercom Doorbell Access Control System Indoor/Outdoor Door BellSilver Condition: Item Type: Wireless Intercom Doorbell Material: ABS Optional Color: Silver, Gold Outdoor-Bell Working Voltage: 4 x AAA Alkaline Battery (4 x 1.5V) (not included), Indoor-Bell Working Voltage: USB cable powered Working Temperature: -20-55 ℃ Wireless Distance: Approx. 200m / 656.2ft (without any obstacle), 5 - 50m / 16.4 - 164ft (with obstacle) Wireless Frequency: 467.6375M Hz Working Time: 4 months, 48 hours IP Level: N/AHow to Install: Outdoor-bell: 1. Remove the battery cover, install 4pcs AAA batteries (not included). 2. Close the battery cover. 3. Press the bell Button, LED around the bell Button light on, it means the device is installed well. 4. Screw up the device. Indoor-bell: 1. Slide power switch to ON. 2. Press the Answer Button, device sound du du..., it means device is installed well. Pair method: 1. Turn indoorbell on and hold Answer Button for about 5s, then release this button, LED flash quickly, now, click the bell Button on the outdoor-bell. 2. When LED on theindoor-bell go out, it means they pair successfully. Indicator for low power: 1. Outdoorbell: LED flash slowly, please replace the battery. 2. Inndoorbell, LED flash slowly, please recharge it 3. For indoorbell, please connect to power source all the time. Installation: Put the tape with double side glue on the wall, then put our door bell on the tape.