This is a pair of Normally open contacts, and NO is an abbreviation of the English word normally open. ; Expansion:; Ac contactor, there are three pairs of main contacts, L1, L2, L3, T1, T2, T3, one end of the main circuit in, the other end out. ; A number of normally open (NO) normally closed (NC) contacts, optional wiring according to the specific function (can not be used). ; Coil contacts, A1 and A2, belong to the load of the control line.