Simple: when a visitor presses the button on the door box, the telephones will ring with a distinctive ring to let you know someone is at the door. Just simply pick up the telephone and you are automatically connected to that door. If you are on the telephone and a visitor comes to your door, you will hear a distinctive call-waiting tone. Press the "flash" key or hook switch your telephone and the built in call-waiting on your DOORBELL FON™ will switch you to the door and place your outside call on hold. When you are finished talking to the door just press the "flash" key or hook switch and connect back to the outside call. When you're done with you call just hang up your telephone. It is that simple.
See spec sheets below for additional information