Electrical connectors allow current to flow through the circuit, where the circuit is blocked or isolated, allowing the circuit to perform its intended function. Some connectors are made into ordinary sockets, which are widely recognized and used in the cable industry.

For many years, the classification of electrical connectors has been confusing, and each manufacturer has its own classification methods and standards. The National Electronics Distributors Association (NEDA, NaTIonalElectronicDistributorsAssociaTIon) presided over the formulation of a set of standards called Levels of Packaging for connector components in 1989. According to this standard, a 4-level connector is commonly used for communication connectors. However, this level is only used to learn and classify connectors. In actual work, connectors are rarely mentioned according to the above levels, but are named according to the appearance and connection structure of the connectors (electric connectors of different structures are named by the internationally detailed specifications) to make specific provisions; Generally speaking, connectors of different structures have different uses). The connection of the communication network usually depends on the media used. Therefore, connectors are usually discussed according to different connection media, connection methods and applications.

 1. Multi-line cable connector

Multi-line cable connectors include DB connectors, DIX connectors and DIN connectors.

(1) DB-type connectors include DB-9, DB-15, DB-25 connectors, used to connect serial devices and parallel cables, divided into male and female heads, DB25 in DB25 is a D-type connector, The number 25 indicates the pin number of the connector. DB25 connector is a common device used for the interface between the microcomputer and the line.
(2) DIX connector: looks like a DB-15 connector. It is realized by the sliding buckle when connecting, and DB15 is fixed by screws when connecting, usually used for connecting thick cable Ethernet.
(3) DIN connector: There are different pins and pin arrangements in the DIN connector. It is usually used to connect Macintosh and AppleTalk networks.

2. Twisted Pair Connector

Twisted pair connections include two types of connectors: RJ45 and RJ11. RJ is an interface that describes a public telecommunications network. , Chao’s upcoming Category 5 or Category 6 cables all use RJ-type interfaces.

3. Backplane, network card and set-top box.

In recent years, the coaxial connector market has developed rapidly. In coaxial exit Ethernet applications that provide high-speed channels, BNC connectors occupy a large number of applications.

In the lower layer of the communication link, BNC series connectors are widely used. Due to its unique bayonet locking method, the BNC series is easy to insert and remove, making it widely used.

Recently, because SMB series connectors can increase the density of connector installation, and because of their excellent performance, they can be used for general commercial applications or military applications, so some users gradually choose to use the SMB type series.

In fact, the same application has multiple options to choose from, and users can choose their own suitable connectors according to their needs.

(1) RJ11 connector: This is a kind of telephone line connector, supports 2 and 4 lines, and is usually used for user telephone line access.
(2) RJ45 connector: The same type of jack is larger than the RJ11 connector, and supports 8 wires. It is a common name for a standard 8-bit modular interface and is commonly used to connect twisted pairs in a network. Because the circuit it uses is a balanced transmitter and receiver, it has higher common-mode rejection.

3. Coaxial cable connector

Coaxial cable connectors include T connectors, BNC connectors and terminating resistors.

(1) T-type connector: used to connect coaxial cable and BNC connector.
(2) BNC connector: BayoNette bayonet barrel connector, used to connect the network segment to the BNC connector. The rapid growth of the communication and computer market and the combination of communication technology and computer technology have become the main factors that stimulate the growth of the demand for coaxial connectors. Because coaxial cables and T connectors rely on BNC connectors for connection, the BNC connector market is optimistic about the industry.
(3) Terminator: The cable requires a terminator. The terminator is a special connector. It has carefully selected resistors that can match the characteristics of the network cable. Each terminator must be grounded. .
(4) Most N-type connectors are used for thick-wire Ethernet. The workstation is not directly connected to the Ethernet, but connects the transceiver to the transceiver through the AUI connector (DIX connector).

RF coaxial connectors are classified according to the connection type, there are three main types:

(1) Thread connection type: such as: APC-7, N, TNC, SMA, SMC, L27, L16, L12, L8, L6 and other RF coaxial connectors. This connector has the characteristics of high reliability and good shielding effect, so it is also the most widely used.
(2) Bayonet connection type: such as BNC, C, Q9, Q6 and other RF coaxial connectors. The connector has the characteristics of convenient connection and fast connection, and it is also the earliest used RF connector connection form in the world.
(3) Push-in push-in connection type: such as SMB, SSMB, MCX, etc. This type of connector has the characteristics of simple structure, compactness, small size and easy miniaturization.

Serial communication is a widely used communication method. In serial communication, both communication parties are required to use standard interfaces. The connectors of the ISDN basic interface all adopt the ISO8877 standard. The standard stipulates that the S interface standard connector is RJ-45 (8 cores), and the middle 4 cores are effective cores. There is no standard for U interface connectors. Some manufacturers use RJ-11 and some use RJ-45. Both of the two cores are effective. The connector of the G.703 interface in the digital transmission network is usually BNC (75Ω) or RJ-45 (120Ω), and sometimes a 9-pin interface is also used. The USB specification (Universal Serial Bus) is a connection standard that provides universal connectors (Type A and Type B) for all USB peripherals to connect to a PC. These connectors will replace traditional external ports such as serial ports, game interfaces, and parallel ports.

In terms of integrated wiring, the past four types, five types and super five types, including the six types of wiring just released, all use RJ-type interfaces. Starting from seven standards, the division of RJ-type and non-RJ-type interfaces has appeared in the history of wiring. The Cat7 connector assembly (GG45-GP45) standard has been passed unanimously on March 22, 2002 (IEC60603-7-7), becoming a standard 7 connector and fully compatible with current RJ-45. [H] The choice of electrical connectors includes environmental conditions, electrical parameters, mechanical parameters and the use of termination methods. Specifically including electrical parameter requirements, rated voltage, rated current, contact resistance, shielding, safety parameters, mechanical parameters, mechanical life, connection methods, installation methods and appearance, environmental parameters, termination methods, etc.

Development situation The electrical connector has the following characteristics:

 1. Development towards miniaturization, high density and high-speed transmission;
2. Towards high performance 1. Develop high frequency technology;
3. The demand for high voltage and high current connectors is also great;
4. The connector is also developing in the direction of anti-interference technology, modular technology and lead-free technology

In the case of the traditional parallel synchronous digital signal rate will reach the limit, high-speed serial mode is a good solution. This makes low-voltage drop sub-signal (LVDS) has become the main level standard for next-generation high-speed signals. The selection of high-speed connectors has also become the main problem to be solved for high-speed signal interconnection.

Several key technologies used in the development of high-speed connectors include: 1. Differential signals for reducing crosstalk, noise-free signals and ground plane technology; 2. In order to adjust the lead of the connector, you can change the input and output The difference in delay caused by the unequal physical distance between them; 3. In order to obtain maximum transmission efficiency, the characteristic impedance value of the connector should match the characteristic impedance of the transmission circuit.