3RH1921-1EA20 First Lateral Auxiliary Switch 2 No Contacts, Screw Terminal, For Contactors. Auxiliary switch block, 2 NO, EN 50005 on the side, 10 mm, screw terminal, Size S0 … S12 for motor contactors, 2-pole, 1st lateral auxiliary switch auxiliary switch SIRIUS 3RH19 for the expansion of auxiliary contacts in the control circuit.This 3RH19 auxiliary switch can be fitted to 3RT1 contactors of sizes S0 – S12 without tools.The 3RH19/3RH29 auxiliary switch blocks are available as versions for front or lateral mounting, with up to four instantaneous contacts or up to two leading NO and NC contacts.