The Heath Zenith
Wireless Doorbell is a great product to update an old or broken door chime system. The Heath Zenith wireless system provides two button/transmitters (with batteries) that emit two different kinds of chimes.
One unit, usually mounted at the front door of the residence, has a classic ďBig BenĒ chime while the second transmitter offers the more familiar ďding dongĒ chime. The two different chimes let you know if a guest is at the front door or if your children or neighbor is at the back door. The transmitters can be programmed by attaching the wires in the chime case to a different channel. The unit is inexpensive and easy to install using either screws or double sided tape to attach it to the wall. It also comes with a five year limited warranty against manufacturers defects.
The Heath Zenith Wireless Doorbell system is available at many leading home center and hardware stores.