1. Versatile communication: this set of wire doorbells comes with two receivers that can be used as a system or can be muted with mute for silent use at any time. inside. 2. System Expandable: Doorbells can be easily expanded to work with almost indoor or outdoor systems. 3. Anti-interference: The doorbell adopts FM wire and is not affected by WiFi interference and does not interfere with other smart devices. 4. Easy to Use: The feature is activated with a push-to-talk button and has volume and channel selection. 5. Waterproof: the unit The exterior is waterproof with a cap design and designed with a charging indicator light that turns green when charging is complete. Specification: Type of item: wire doorbells Material: ABS Charging base: 12 V-450 mAh : key of SET: the unit is not functional VOL: Volume selection CH: Channel selection Waterproof cover: waterproof exterior Charging indicator : red (charging) green (full) Outer and inner door battery: 2500mAh 18650 lithium battery (built-in) Package content : 1 x unit outdoor 1 x outdoor unit interior 1 x base unit exterior 1 x charging base 1 x charging cable 1 x manual 1 x pack of screws 2 x sticker Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.