The Detex AT-5200 (ES5200) Tailgate Detection Systems assure that only one individual enters a secured doorway for each authorized card read. Compatible with most card reader technologies, the AT-5200 is easy to retrofit. This unique and cost effective optical security system, which uses infrared sensor beams to detect tailgating, is perfectly suited for areas requiring tighter security. For digital voice annunciator, specify AT-5600 (ES5600).