On the CS 1000 endpoint, Call Waiting notifies a telephone user on an established call on a Single Call Arrangement DN button (both internal or external calls), that an external call is waiting to be answered. When an external call comes, and the user is on a call, the Call Waiting lamp flashes and a buzz sounds through the speaker.

With the Communication Manager, the endpoints have more than one line appearance for the calls, and the call is presented to the second, third, or fourth appearance button.

The Device Adapter uses the added call appearance button to provide call waiting. Bridged appearance buttons (shared with other users) do not get call waiting.