Siemens 3RH1921-1FA22 Electrical Contact. Siemens Auxiliary Mounting Block 4-Pole 230 VAC 0.41 A 4 Contacts 2NO-2NC For Use With: S0 to S12 Frame 3RT1.3 to 3RT1.7 3RT10.2 and 3RT11 Contactors Screw 38 mm H x 44 mm W x 51 mm D. Additional Description: SIEM-3RH1921-1FA22 (N) AUXILIARY FRONTS0-S122NO&2NC. Catalog Description: MOUNTING BLOCK DIN EN 50005 4-POLE2NO+2NC.