Wireless Doorbell: 2NI1 doorbell, 2 indoor units also available as handheld radios, effective range of 1KM / 3200FT in open environments, strong and stable wireless signal will ensure you don't miss any visitors, 3 adjustable volume levels (60dB-90dB). New Upgrade: Wireless doorbell with built-in 2000mAh battery, outdoor unit - rechargeable directly from the DC port. The outdoor wireless doorbell can be used for approximately 6 months. Indoor unit - rechargeable via the base. 2-way voice intercom: Doorbell intercom - Pressing the "TALK" button directly between the two indoor units enables voice intercom communication, a feature that easily facilitates family care for elderly and sick individuals. It can also be used like a family voice intercom system. The outdoor wireless doorbells have a sealed, waterproof design; wet or rainy days will not affect the operation of the wireless doorbell (cannot be submerged in water). Two mounting options: adhesive and screw-on. Depending on the frequency of use, you may need to recharge the indoor unit once every 3-5 days, and it is recommended to return it to the charging station after use; recharging is possible at any time.