Expand your Plug-In Extend-A-Chime System, sold separately, by placing this extra chime module in an area of your home that your existing chime previously couldn't be heard. The extra chime module can even have a different chime sound to distinguish visitors at the front or back door. Simply plug this into any standard outlet to receive a wireless signal form the Extend-A-Chime System, no batteries required.Now you'll never miss an important visitor because you can't hear the doorbell! This Extra Chime Module works with the Plug-In Extend-A-Chime (not included) to expand an existing wired doorbell to be heard in any part of the home. The transmitter connects onto the low-voltage screws in the existing doorbell. Plug the doorbell receiver into any 110V electrical outlet. Hear the doorbell in all parts of the home-basement, second floor, or the attic.