Abstract: A security door and system for installation as the entrance and exit to a building or office to automatically control the passage of persons therethrough and to trap certain persons therein comprising a vestibule having side walls and oppositely disposed doors which open and close automatically under the control of photocell detectors and time delay relays. The photocells energize motors which open a respective door through which the person may enter the unit. After a predetermined time delay the opposite door opens. An emergency switch is provided to override the automatic control so that a person can be trapped and detained within the vestibule if desired or necessary.