What is Wireless Doorbell？

A wireless doorbell system includes a chime box receiver and a doorbell transmitter. 

The transmitter attached to the outside of the home, sends a radio signal to the inside of the home where the receiver is located. ...

Because no wiring is needed with a wireless doorbell, two or more receivers can be used.

What is the difference between a wired and wireless doorbell?

There are two main types of doorbells: wired and wireless.

The traditional door bells involve complex wiring systems that you may need professional help to install and set up the doorbell device. 

Wireless doorbells operate on batteries or electricity and do not require wiring.