Self-powered wireless doorbell: no battery, no wiring; easy to install and environmentally friendly. Long range: Maximum range of 200 meters in open area without obstacles. The effective distance across 3 volume levels ensures you can hear the chime and respond promptly. The design is simple and compact, and this device can also function as a beeper (sound signal), suitable for use by elderly individuals, children, and others. The wireless, battery-free doorbell offers 38 different chimes and 3 adjustable volume levels to suit your preferences. Easy to install and use: The transmitter can be installed in two ways. Use the included tape or screws to secure the transmitter to the door frame. Plug in the doorbell receiver to activate. Box contents: 1 x transmitter, 1 x receiver