1、 Classification of connectors: 1) Classified by appearance: circular electrical connectors, rectangular electrical connectors. Circular electrical connectors are the most commonly used in military equipment (aviation, aerospace). Rectangular electrical connectors are more commonly used on printed circuit boards in electronic devices. 2) According to structure: according to connection method: threaded connection, bayonet (quick) connection, lock connection, push pull connection, straight plug connection, etc; Terminate according to the contact body: crimping, welding, winding; Fix with screws (caps); Classified by environmental protection: environmentally resistant electrical connectors and ordinary electrical connectors 3) Classified by purpose: sealed electrical connectors, high-temperature electrical connectors, separated electrical connectors, filter electrical connectors, power electrical connectors, and electrical connectors for printed circuit boards Secondly, the quality of connector inspection is good or bad. 1. The manufacturer inspects connectors. Firstly, we understand the following basic standards for the appearance of good connectors. The connectors are composed of terminal rubber shells and needle seats, and we divide them into pre assembly and post assembly inspections. Pre assembly inspections include missing materials, burrs, shrinkage, deformation, color difference, dirt, blockage, indentation, uneven/deformed partition boards, sticking points, sinking/deviation or breakage Incorrect/No PIN Identification After Assembly Inspection: Check if there is any gap between the copper shell/iron shell and the rubber shell, if the iron shell/copper shell is deformed, if the buckle is not pressed in place/deviated, if the rubber shell is damaged, if the left and right hooks are not installed in place (the exposed dimensions of the hooks at both ends are not consistent), press the hooks several times by hand to confirm whether the left and right hooks are normal, and if there is elasticity. These are all factors that the connector manufacturer eliminated during product inspection, and remove the defective products inside. These are all the testing steps in the manufacturer's quality inspection. 2. Some personal detection connectors may appear to be fine on the surface, but they are damaged internally. Experienced people can directly determine the quality of connectors by touching, smelling, and looking. 1. Touch and feel with your hand whether the production of the connector is meticulous. If there is a noticeable roughness on the surface and the lifespan is not guaranteed, there is a huge difference in safety between the connector and high-quality products. 2. Smell, some manufacturers may add fragrance to mask the taste of inferior materials, so when encountering products with fragrance, it is necessary to carefully consider them. 3. Look, if you see connectors and sockets heavily oxidized on the metal surface, which is basically a gray color with similar degrees, these are all quality issues that can affect the welding quality. Generally, connectors that have not been used will not show oxidation or damage in appearance. Connectors are essential components in electronic devices, and when observed along the path of current flow, you will always find one or more connectors. The form and structure of connectors are ever-changing, and there are various forms of connectors depending on the application object, frequency, power, application environment, etc. It plays an important role in electronic engineering construction, ensuring smooth circuit flow, and is therefore widely used