No Battery Required: Our wireless doorbell transmitter uses the unique technology. When you press the button, the kinetic energy is converted into an electrical signal that rings your doorbell wirelessly. No more worrying batteries. More convenient, more energy-saving and more practical than the old one. 45 Beautiful Chimes and Melodies: Offers 45 classic melody chimes with adjustable volume control and diverse selection to meet your needs. 4 adjustable volume levels from 0dB to 90dB, which is loud enough for the elderly to hear; enjoy pleasant melodies every time someone rings your doorbell. The LED indicator gives you a visual form of notification (a great feature for the hearing impaired). Long Wireless Range: With 150M/500FT wireless range, 2 plug-in receivers included, won't interfere with other equipment in your home or your neighbors'; ensures you'll never miss a visitor even if you're a few rooms away or on another floor. Ideal for large homes, warehouses, offices, etc. Memory