Also known as the FLO-SAFE Seismic Safety and Management System the FS2100 employs an onboard PLC, or in some cases a programmable relay, to verify the existence of a line break before shutting down valves. This answers the greatest complaint from fire departments who strongly urge water districts not shut down water supplies after a severe earthquake. When the seismic sensor on board the FLO-SAFE trips at a seismic event, no valves are shut down. Instead a timing sequence begins during which the PLC compares water flow rates to preset parameters. If the rates do not exceed those limits during the timing sequence, the sensor resets. If flow rates do exceed the limits, only then are valves shut down. The logic behind this is that after a period of time (e.g.. 15 minutes), any increase in flow will most likely be the result of fire departments using water. Any increase during those first few minutes however will probably be caused by breaks in the pipelines.