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It also assumes that you have full access to all features and the public telephone network. Making Calls Internal Calls: To make a call to another extension, simply dial the number. If the number is busy, you can use Ring Back When Free as below: 1. Dial any digit and hang up. 2. When the extension you called is free, your phone will ring (a burst of three rings). 3. Lift the handset and the extension is called automatically. External calls: To make an external call, either dial the number (ther