The ELK-6023 Wireless Recessed Door Sensor is the ultimate wireless security device for discriminating customers. It mounts into a 3/4” drilled hole in a wooden door jamb and becomes nearly invisible once the door is closed. It features Elk’s Industry Leading Two-Way Technology with positive signal acknowledgment, extended range, and long battery life. It works with Wireless Transceivers and Controls that accept Elk’s two-way technology; such as, the ELK-M1XRFTWM. Each time the 6023 transmits it sends a unique TXID identifier and a Loop number.