Knows that it's a charger and tells the T28 phone that it's hooked up and automatically changes the profile to home or office. It even keeps track of different cradles (home and office!)One warning if you have two T28's at home (e.g. husband and wife) keep track of which charger goes to which phone otherwise they keep trying to reset and override causing an error (a dollop of pink paint on the base of one of the chargers made it 'hers' and solved the problem.) Well worth the extra money over the ordinary travel charger.