Detailed Product Description: The operating principle bases on a free-floating magnetic piston, which responds only to the motion of fluid within the pipeline, not to static or system pressure. In the presence of fluid flow, controlled movement of the piston actuates an external hermetically sealed reed switch, thus producing the required signal which can be used to actuate audible or visual alarms as well as relays or other. Control of various amounts of flowing liquid in a small-scale process. Detection of amount of flowing liquid in a pump, hot water and warm water supplies.