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 Response Card through two-way communication. * Successful transmissions are acknowledged on the participant"s keypad via a three second long visual green light signal.