You can answer another extension that is ringing by using the Ring Intercept Feature.
Simply dial, ** + the extension of the phone that is ringing.
For example, if extension 101 is ringing, you would dial **101 to intercept and pick up the remote extension.
Example (T57W) : To intercept a call that is currently ringing ext 709, you would dial **709 and then press call.
Example (T54W) : To intercept a call that is currently ringing ext 706, you would dial **706 and then press the call button.