1) There are two kinds of circuit board connectors: single lead and multi lead, as shown in Figure 119（ a) For single lead connector, (b) for multi lead connector. They are characterized by flexible use, small occupation area, easy to plug, pull and so on. The structure of the utility model is that the socket is provided with a connecting piece (metal piece) and the plug is provided with a lead wire connecting pin. For the multi lead connector, in order to prevent the plug from being inserted in the wrong direction, each socket has a positioning block. The plug can only be inserted into the socket in the specified direction, and can not be inserted into the socket in case of reverse or displacement. When the connector is used, the socket part needs to be directly welded on the copper foil printed circuit of the circuit board, the lead wire is led out on the plug, and then the plug is inserted into the socket to connect the circuit.