"A few" is to see the valve has several working states, it can be said to be a few, such as the pneumatic component symbol, on the diagram represents the valve body of the square (there are arrows or T line) a few is a few.

"Several" means that there are several points on one of the squares (the point where it intersects the arrow line and the t-line).

Several: if according to the number of valve switching port (including the input port, output port, exhaust port) to classify, there are two valve, three valve, four valve, five valve.

Several: the working position of valve core hereinafter referred to as "a", the valve core has several work (switch) becomes a few valve position. The valve core has three working position of the valve become three valve. When the valve core is in middle position, all his is closed, said the middle closed, the outlet and the vent all through middle pressure type, if the outlet is connected with input port is referred to as the intermediate pressure.

"On" and "on" and "bit" of solenoid valve is an important concept of pneumatic reversing solenoid valve. Different "on" and "bit" constitute different types of pneumatic reversing solenoid valve.

The so-called "two-way valve", "three-way valve", "four-way valve" refers to the valve body of the reversing valve has two, three, four are not connected and can be connected with the system of different oil pipes or gas we connected to the interface, different oil channels/gas lines can only be through the valve valve port switch to communicate.

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Annex：