The RL3000 is a thicknet to AUI ethernet transciever manufactured by American Photonics Incorporated in 1991. It measures about 2.5" high by 4.5" wide and 1 inch deep. It has an AMP 228752-1 30 VDC 100mA Class 2 coaxial vampire tap to connect into the thicknet and the standard 13 pin AUI adapter on the side for ethernet.