Siemens auxiliary contactswitch for sirius 3rv1 transverse and lateral siemens 3rv1901 1a the siemens sirius 3rv1 circuit breakers also known as msps motor starter protectors have three main contact elements in order to achieve maximum flexibility auxiliary switches can be supplied separately these components can be fitted as required on the switches without using toolsthis lateral auxiliary contact block 3rv1901 1a order code 55 7179 is a side mounted auxiliary contact with 1 no a