Two position three-way valve, two position five way valve, and two position five way solenoid valve have one inlet hole (connected to the air source), one forward action air hole, and one reverse action air hole (providing one forward and one reverse action air source to the target device respectively), one forward action exhaust hole, and one reverse action exhaust hole (equipped with a muffler). For small automatic control equipment, industrial rubber hoses with a diameter of 8-12mm are generally used for the air pipes. Electromagnetic valves are generally selected from Japanese SMC (high-end, but small Japanese products), Taiwanese Yadeke (affordable and of good quality), or other domestic brands.
In electrical terms, two position three-way solenoid valves are generally single controlled (i.e. single coil), while two position four-way solenoid valves are generally dual controlled (i.e. dual coil). The voltage level of the coil is generally DC24V, AC220V, etc. Two position three-way solenoid valves are divided into two types: normally closed and normally open. The normally closed type refers to the air circuit being disconnected when the coil is not powered, while the normally open type refers to the air circuit being connected when the coil is not powered. The operating principle of a normally closed two position three-way solenoid valve is to energize the coil and connect the air circuit. Once the coil is powered off, the air circuit will be disconnected, which is equivalent to "inching".