The type 3171 vibration switch is a low-cost, vibration-sensitive switch for the protection of rotating and reciprocating machinery. It is adjustable to operate above the machine's normal running levels of vibration, activating machine shut-down circuits and/or alarms. Once operated the internal micro switch remains latched until reset. The type 3171 vibration switch, with its low frequency response is ideal for detection of mass imbalance on most machines. It is inherently insensitive to high frequency components and those caused by external knocks, etc. The 3171 vibration switch is responsive to vibrations in all directions. The type 3171 vibration switch is reset by depressing a button on the bottom face (see diagram below) and for the 3171S model, also by temporarily energising an internal solenoid. Adjustment of the vibration trip level is made externally at the top of the unit by rotating a sealed control. A single pole vibration switch uses one internal micro switch for switching off machinery when an increase in peak acceleration is detected. A double pole vibration switch has an additional internal micro switch which operates simultaneously with the first one. Two micro switches give the use of redundancy for increased safety and can also be used for monitoring the state of the vibration switch.