This is a 12V 50mA 4.5x1.8x3.5mm 4Pin Rectangle Button SPST Tactile Switch SMD. This switch features reliable dome contact technology and strong tactile feedback. A tactile switch allows electricity to flow in an electrical circuit by manually pressing the operating section. The switch is used to supply an input signal to actuate a device or equipment. These switches are commonly used in many consumer and industrial electronic devices.