SIRIUS safety relay basic unit 3SK2 series 20 f-di, 4 f-dq, 2 dq, 24 V DC parameterizable via SIRIUS safety es width 45mm spring-type terminals up to sil3 (iec61508) up to performance level e (iso 13849-1) 3sk1 output expansions and 3rm1 fail-safe motor starter connectable via device connector