An electrical connector is a device for joining electrical circuits together. Most electrical connectors provide an electrical connection that can be relatively easily established and separated, but connectors are also available to facilitate permanent connections. There are hundreds of types of electrical connectors. In computing, an electrical connector can also be known as a physical interface.

Types of electrical connectors

A terminal is a simple type of electrical connector that connects two or more wires to a single connection point. Wire nuts are another type of single point connector.

Terminal blocks of various types.

Terminal blocks

Terminal blocks (also called terminal boards or strips) provide a convenient means of connecting individual electrical wires. They are usually used to connect wiring among various items of equipment within an enclosure or to make connections among individually enclosed items. Since terminal blocks are readily available for a wide range of wire sizes and terminal quantity, they are one of the most flexible types of electrical connector available. Some disadvantages are that connecting wires is more difficult than simply plugging in a cable and the terminals are generally not very well protected from contact with persons or foreign conducting materials.

One type of terminal block accepts wires that are prepared only by removing (stripping) a short length of insulation from the end. Another type accepts wires that have ring or spade terminal lugs crimped onto the wires. Printed circuit board (PCB) mounted terminal blocks allow individual wires to be connected to the circuit board. PCB mounted terminal blocks are soldered to the board, but they are available in a pull-apart version that allows the wire-connecting half of the block to be unplugged from the part that is soldered to the PCB.

Crimp-on terminals

Most types of crimp-on terminals (or lugs) are attached to wires to allow the wires to be easily connected to screw terminals and fast-on or quick-disconnect terminals. There are also crimp-on terminals for connecting two wires together either permanently or with disconnect capability. Crimp-on terminals are attached by inserting the stripped end of a stranded wire into the tubular portion of the terminal. The tubular portion of the terminal is then compressed tightly around the wire or crimped by squeezing it with a special crimping pliers.

Insulation displacement connectors

Since stripping the insulation from wires is time-consuming, many connectors intended for rapid assembly use insulation-displacement connectors so that insulation need not be removed from the wire. These generally take the form of a fork-shaped opening in the terminal, into which the insulated wire is pressed and which cut through the insulation to contact the conductor within. To make these connections reliably on a production line, special tools are used which accurately control the forces applied during assembly. If properly assembled, the resulting terminations are gas-tight and will last the life of the product. A common example is the multi-conductor flat ribbon cable used in computer disk drives; to terminate each of the many (approximately 30) wires individually would be slow and error-prone, but an insulation displacement connector can terminate all the wires in (literally) one stroke. Another very common use is so-called "punch down" blocks used for terminating telephone wiring.

Insulation displacement connectors are usually used with small conductors for signal purposes and at low voltage. Power conductors carrying more than a few amperes are more reliably terminated with other means, though "hot tap" press-on connectors find some use in automotive applications for additions to existing wiring.

Plug and socket connectors

Plug and socket connectors are usually made up of a male plug and a female socket, although hermaphroditic connectors exist, such as the original IBM Token Ring LAN connector. Plugs generally have one or more pins or prongs that are inserted into openings in the mating socket. The connection between the mating metal parts must be sufficiently tight to make a good electrical connection and complete the circuit. When working with multi-pin connectors, it is helpful to have a pinout diagram to identify the wire or circuit node connected to each pin.

4-conductor hermaphrodite connector for token-ring attachment.

Detail of mating surfaces of hermaphrodite connector.

px150|right|Transistor switch module with large screw connectors and small fast-on connectors.

Component and device connectors

Electrical and electronic components and devices sometimes have plug and socket connectors or terminal blocks, but individual screw terminals and fast-on or quick-disconnect terminals are more common. Small components have bare lead wires for soldering. They are manufactured using casting