Apollo-Wireless Doorbell Music Door Bell Digital Doorbell 1 Wireless Transmitter Push Button + 1 Wireless Doorbell 1 x Doorbell Push Button Transmitter + 1 x wireless Doorbell You can install the remote buttons in one location. such as front door. Back door. etc. Flash light turns on when guest presses the remote button. With double side stickers at the back side of the remote button. very easy to install. The ultra-distance remote control (100 meters long) meets the need of various buildings.