ADTEC AB98-54B Input/Output 48-point TTL Level Parallel Board https://cpi-tec.jp/adtek/seihin/ab98/ab98-54/index.html This product, the AB98-54B, is an expansion board that adds TTL level parallel input/output functionality to the NEC Personal Computer PC-9800 series. By installing it in the expansion slot provided in the PC-9801 main unit or I/O expansion unit, 48-bit TTL level parallel input/output functionality is added per board.