US Patent 6966147 Automatic pet door

An automatic pet door system is disclosed. The automatic pet door system has a rectangular frame mounted between studs of a wall defining a passage for entry and exit of a pet. A door slidably moves within the frame between a lower closed position for closing the passage and an upper open position for opening the passage. The door is lifted by a drive means having a motor pulling a cable attached to the door. The motor is energized by a control means in response to a signal received from a magnetic transmitter worn by a pet when the pet approaches the door. A locking means prevents movement of the door upwardly from the closed position unless the door is moved by way of the drive means.