Siemens 3RH2911-1FA22 Auxiliary Switch Block

The auxiliary switch block, also known as auxiliary contact element, add-on switch, or additional contact set, with type number 3RH2911-1FA22 from Siemens, is an electrical switching device for extending switching functions. It features a configuration of 2 normally open (NO) and 2 normally closed (NC) contacts, also referred to as 2S+2O or 2NO+2NC. The device has dimensions of 10 x 5 x 5 cm and weighs 0.06 kg. Auxiliary switch blocks are used to increase the number of available contacts on main switching devices like contactors or circuit breakers, and are employed for realizing control, signaling, and interlocking tasks in electrical systems. Typical applications are found in mechanical and plant engineering for controlling machine sequences, and in automation technology for monitoring operating statuses and implementing safety functions.

2S+2O / 2NO+2NC