This Siemens 3SB3500-1AA20 emergency stop pushbutton and holder has a red 60 mm diameter head mushroom-shaped plunger that pushes to lock and twists to unlock for maintained operation. When used with the Siemens 3SB3 series contact block (not included), the plunger forcibly opens the normally closed (NC) contacts for use in safety circuits. The pushbutton mounts through a 22.5 mm diameter control panel hole. This emergency pushbutton conforms to the European Committee for Electrotechnical Standardization (CENELEC) EN 418 standard for emergency stop equipment, such as in manufacturing process control systems.Pushbutton switches make or break electrical connections as part of a system that controls a process, such as a manufacturing line. Indicator lights with labels or color-coded caps are used to display the current state of a process, such as "completed." The pushbutton unit is composed of a pushbutton actuator for making or breaking electrical connections, a holder for securing the actuator to a control panel and for housing a light, and one or more contact blocks for connection to electrical wiring. Contacts within a contact block can be normally open (NO) or normally closed (NC), so that pressing the button starts or stops a process. Holders accommodate a range of control panel thicknesses and may include lamps to illuminate the button. Pushbutton actuator head types include mushroom, flat-surface, raised-surface, and key-operated, and may be illuminated, color-coded, and labeled. According to the requirements of an application, actuators may operate only as long as the button is held or they may lock into position when pushed and unlock when pulled or twisted. Pushbuttons and indicator lights are used in applications such as manufacturing process controls and as emergency shutoffs in industrial workplaces.Siemens manufactures electronic products for building automation, industrial drives, lighting, energy generation, medical equipment, and rail transportation. The company, founded in 1847 and headquartered in Munich, Germany, meets International Standards Organization (ISO) standards 14001, 9001 and TS 16949.What"s in the Box?Red pushbuttonHolder