The Videx door-entry system uses a person’s existing telephone to speak to a caller at the front door and open it. The system consists of a front door unit and an interface to the telephone line. When a caller rings the door bell the telephone rings twice as fast as normal. This allows the occupant to distinguish between a call to the front door and a normal incoming telephone call. When they answer the phone they can speak directly with the caller at the door. To let the caller in they press button 9 on the phone. This releases an electric lock and the caller can push open the door.