Wireless door bell

http://www.hoelectric.com/Electrical-Services-Massachusetts/Basic-Information-About-Doorbells-Buzzers-or-Chimes.html
Video
http://www.ehow.com/video_4418489_install-wireless-doorbell.html
This video is about installing a wireless door bell. First he turned off the electricity. Then he started to describe the braker box. Tell about different switches and how much power it has. I also found out on this site that the electrical was invented in 1831 Joseph Henry. The device that send the signal to and from the door bell is called a chime or buzzer. On my link it leasted the materials. On my link it had different ways to wire the chimes with multiply chimes and etc.