A pet door unit allowing entry to and egress from a dwelling of an animal includes a pet door provided with a latch. The pet door is mounted for movement to allow passage of an animal when the latch is disabled. The pet door unit includes an animal detector for detecting an animal seeking passage past the pet door. A controller allows selection of a permitted passage condition. A disabler selectively disables the latch. Other arrangements described include systems for controlling entry and exit for different animals in different time frames, systems that detect an animal by a tag carried by the animal, systems that detect a door, systems that detect whether an animal has actually passed through the door and in which direction, and systems that record time and direction of passage, a preferred coil geometry for tag detection, and a preferred latch.