Intercom Doorbell - The doorbell horn is loud, the volume is adjustable and the ringtone is changed, the quality The intercom sound quality is clear and it can be used for mobile intercom. Strong Signal - The doorbell kit adopts universal frequency, the signal transmission distance is long, in the open area, the maximum signal transmission distance can reach 300 meters. Code Pairing - With the code pairing function, one outdoor doorbell can be used for 2 indoor multi-doorbells without interfering with each other. No interference with operation. Exquisite Doorbell Kit - The doorbell kit is exquisite, compact, beautiful and powerful. It is easy to install and stick to the wall directly with glue. Power Source - The outdoor unit is easy to install and remove the battery. It uses 4 AAA batteries (not included) and the outdoor unit The internal USB port is used with an external USB data cable.