Wet alarm valve above a pressure gauge pressure below a pressure gauge no pressure which represents what?

By definition, the upper table represents the system end pressure, the lower table represents the water supply end pressure, if one of the table value is inaccurate, either the table is responsible for the end of no water or insufficient pressure, or the pressure gauge is bad. Second table atlas 04S206 is connected through the check valve, but in practice, sometimes not connected.

About the value of the two tables, generally speaking, should not be a big difference, according to the atlas explanation, the two tables are connected with check valves, the role of the water supply to the system end to make up the pressure, to prevent the upper and lower pressure difference is too large, causing false alarms. Therefore, if the pressure difference between the two tables is large, excluding the respective system water pressure is insufficient, the pressure gauge is bad, that is, they are blocked in the middle of the check valve, because the value of the two tables should be the same.