ResponseCard RF Lightweight, compact, grey "credit card" format. Dimensions: 3.3" L x 2.1" W x 0.3" H. Weight: 1.0 oz (with batteries). Durable, rugged case ensures maximum longevity under extreme conditions. Will not interfere with other technologies. Participants receive answer confirmation on their ResponseCard through two-way communication. Successful transmissions are acknowledged on the participant's keypad via a three second long visual green light signal.