device: 7SL87 differential/distance protection, 1 /3-pole dual-end fault protection, expandable housing type: surface mounting; BI: 31; BO: 21 (11ST + 6F + 0HS + 4P); I: 4 (protection); U: 4 ( standard); measuring transducer inputs: 0 (20 m A or 10 V, fast), 0 (20 m A, normal); housing width: 5/6 x 19''; modules in 19" row 1: IO 202, PS201, IO204, IO204, PS20 4; modules in 19" row 2: ; LEDs/push-buttons: 8 push-buttons /LEDs(NE)+48 LEDs; operation panel: integrated; key switch: with; display type: large display; front design: standard;