Siemens 3SB3403-0A Contact Block

Siemens 3SB3403-0A is a front-plate mounted contact block for the Sirius 3SB3 operator family, delivering two contacts in a single module: 1 normally open (NO) and 1 normally closed (NC). It is designed to attach to a 22 mm 3SB3 actuator/indicator and uses spring-type terminals for wiring, with a mounting depth of 50 mm. When the actuator is operated, the NO contact closes to energize a circuit while the NC contact changes state accordingly; the NC contact opens automatically when the contact block drops out from the actuator, ensuring predictable signaling behavior. This accessory is used in control panels to provide dual-path signaling or interlock functionality from one pushbutton or indicator, and Siemens catalogs list a gold-plated variant (3SB3403-0AA) for applications requiring enhanced durability of the contacts. The part is cataloged as 3SB3403-0A and sits within Siemens’ 3SB3/Signum line of front-plate contact blocks that complement pushbuttons and indicators in industrial control and automation applications.