Siemens 3SB3 647-0AA21 Push Button

Siemens 3SB3 647-0AA21 is a 22 mm metal-round complete unit illuminated push button with a flat red actuator, designed for panel mounting in industrial control applications. This momentary-contact device operates from 24 V AC/DC and provides a 1 normally open plus 1 normally closed (1NO+1NC) contact arrangement, with an integrated LED indicator to show status. The unit uses screw terminals for wiring and includes a holder, enabling straightforward installation in standard enclosures while maintaining a compact, low-profile appearance. Its red illumination and flat-button form factor make it suitable for signaling, stop/start controls, or status indicators within the Siemens SIRIUS 3SB3 signaling family.