The 5800TM Transmitter Module is designed to be used in conjunction with one or more wireless bidirectional devices. The 5800TM is compatible with any control panel that is also equipped with a 5800 Series RF receiver. It transmits the information to be displayed on, or sounded by a wireless bidirectional keypad. Features -Sends system status/message back to bi-directional wireless devices -Allows upsell opportunities to add bi-directional wireless devices to existing RF system -Gives homeowners system status before they enter the premises -Dimensions: 4-1/8" H x 2-1/4" W x 7/8" D