The Siemens 3RA9012-5BN40 is a mushroom-head pushbutton with an illuminated red actuator, push-pull operation, and two normally-closed (2NC) contacts terminated via cage clamp connection. It's part of the SIRIUS accessory family, designed for control stations and panel-mount E-stop or reset applications where a maintained-pull-to-reset action is required.
The cage clamp connection accepts solid or ferruled stranded wire without screw tightening — a time-saver on the panel-wiring bench and more vibration-resistant than a screw terminal in a nacelle cabinet.