In information science, connectors, normally called “input-output connectors” (or I/O for short), are interfaces for linking devices by using cables. They generally have a male end with pins protruding from it. This plug is meant to be inserted into a female part (also called a socket), which includes holes for accommodating the pins. However, there are “hermaphroditic” plugs which can act as either male or female plugs, and can be inserted into either one.


Input/output connectors: The computer’s motherboard has a certain number of input-output connectors located on the “rear panel.”


Most motherboards have the following connectors:

  1. Serial port, which uses a DB9 connector, for connecting older devices;
  2. Parallel port, which uses a DB25 connector, mainly for connecting old printers;
  3. USB ports (1.1, low-speed, or 2.0, high-speed), for connecting more recent peripherals;
  4. RJ45 connector (called the LAN port or Ethernet port), for connecting the computer to a network. It interfaces with a network card built into the motherboard;
  5. VGA connector (called SUB-D15), used for hooking up a monitor. This connector interfaces with the built-in graphics card;
  6. Jacks (Line-In, Line-Out and microphone), for connecting speakers or a hi-fi sound system, as well as a microphone. This connector interfaces with the built-in sound card.


Pin layout: The pins and holes in connectors are usually linked to the electric wires which form the cable. The pin layout describes which pins couple with which wires. Each numbered pin generally corresponds to a wire within the cable, but sometimes one of the pins is left unused. Additionally, in some cases, two pins may be linked to one another; this is called a “bridge.”


5-pin DIN plugs: A DIN (or DIN5) connector is a plug with 5 pins, formerly used to connect keyboards to computers:


The DIN5 connector has been made obsolete by PS/2 and USB connectors.




Coaxial Cable Connectors: The most common type of connector used with coaxial cables is the Bayone-Neill-Concelman (BNC) connector. Different types of adapters are available for BNC connectors, including a T-connector, barrel connector, and terminator. Connectors on the cable are the weakest points in any network. To help avoid problems with your network, always use the BNC connectors that crimp, rather screw, onto the cable.


Thinnet and Thicknet both use BNC (Bayonet-Neill-Concelman or British Naval Connector) connectors to hook up the cables to computers.

The following connectors are in the BNC family:

  1. BNC cable connector: this is soldered or crimped to the end of the cable.
  2. BNC T-connector: this connects the computer’s network card to the network cable.
  3. BNC Extender: this joins two coaxial cable segments to form a longer one.
  4. BNC terminator: this is placed at each end of a cable in a Bus network to absorb interference signals. It is connected to earth. A bus network cannot function without them. It would stop working.



In the RJ-45 connection, the cables used are called twisted pairs, as they are made up of four pairs of wires braided together. Each pair of wires is made up of a solid-colored wire and a wire marked with stripes of that same color. It is highly recommended to use a category 5 cable between 3 and 90 metres long. There are two wiring standards which differ in the position of the orange and green pairs, defined by the Electronic Industry Association/ Telecommunications Industry Association: The two wiring standards are TIA/EIA 568A and TIA / EIA 568B.


It can be noted that connector 1, at left, as seen on a female plug (network card or wall outlet) and at right on a male plug, connector pointing outwards, contacts upwards.


Crimping a RJ45 cable: The RJ45 cable is a standard cable which has four twisted pairs of colors. It is easy to crimp a RJ45 cable and make it into a straight cable or cross the cable as required. To make a straight cable, the ends must be crimped in the same way at each end. When making a crossover cable, some wires of certain colors have to be reversed.


Items Required

  1. A reasonable length FTP cable.
  2. Two RJ45 tips.
  3. A clip crimp.


Steps in crimping a RJ 45 cable

Strip the cable to 2 cm at each end and separate the strands.


They are usually divided into 4 twisted pairs of colors:

  1. Orange / orange-white.
  2. Green / green-white.
  3. Blue / white and blue.
  4. Brown / brown-white.


Making a straight cable

To make a straight cable, the tips must be crimped typically the same way at each end by respecting the twisted pair size.


In general, the code used is:

  1. orange-white.
  2. orange.
  3. green-white.
  4. Blue.
  5. blue-white.
  6. Green.
  7. brown-white.
  8. brown.


Making a crossover cable

For a crossover cable, swap 1 with 3, and 2 with 6, in the list above. This gives:

  1. green-white.
  2. green
  3. orange and white.
  4. Blue.
  5. blue-white.
  6. orange.
  7. brown-white.
  8. brown.


The standard EIA / TIA 568 (A & B)

Straight cable

  1. white-green / white-green.
  2. green / green.
  3. white-orange / white-orange.
  4. Blue / blue.
  5. white-blue / white-blue.
  6. Orange / orange.
  7. white-brown / white-brown.
  8. brown / brown.


For crossover cable 10/100baseT

  1. white-green / white-orange.
  2. Green / orange.
  3. W white-orange / white-green.
  4. Blue / blue.
  5. white-blue / white-blue.
  6. Orange / green.
  7. white-brown / white-brown.
  8. brown / brown.


To complete crossover cable or cross gigabit On Gbic 1000BaseT eg

  1. white-green / white-orange.
  2. Green / orange.
  3. white-orange / white-green.
  4. Blue / white-brown.
  5. white-blue / brown.
  6. Orange / green.
  7. white-brown / blue.
  8. Brown / white-blue


Many Gigabits (10/100/1000 multi speed) are auto MDI / MDIX and automatically adapt to the type of cable connected.



The RJ11 connector (RJ for Registered Jack) is the most commonly used connector for telephone lines. It is similar to the RJ45 connector, but smaller.

When found on a computer, the RJ11 is generally meant for a modem.


RJ-11 Plug Wiring

The most familiar registered jack is probably the RJ11. This is a modular connector wired for one plain old telephone service line (using two wires out of six available positions), and is found in most homes and offices in most countries of the world for single-line telephones. Essentially all one, two, and three line analog telephones made today (2009) are meant to plug into RJ11, RJ14, or RJ25 jacks, respectively.


The six-position plug and jack commonly used for telephone line connections may be used for RJ11, RJ14 or even RJ25, all of which are actually names of interface standards that use this physical connector. The RJ11 standard dictates a 2-wire connection, while RJ14 uses a 4-wire configuration, and RJ25 uses all six wires. The RJ abbreviations, though, only pertain to the wiring of the jack (hence the name “registered jack”); it is commonplace but not strictly correct to refer to an unwired plug connector by any of these names. Typically you’ll find the RJ-11 and RJ-14 on your Plain Old Telephone Service (POTS) though your RJ25 typically is found in an Integrated Services Digital Network (ISDN) Line. It is the communication standards that lets telephone lines to carry digital, voice, video, and network services.



A Tee connector is an electrical connector that connects three cables together. It is usually in the shape of a capital T. It is usually used for coax cables and the three connector points can be either female or male gender, and could be different or the same standard, such as F type BNC or N type.

Tee connectors can be used to split radio frequency power from a cable into two. It could be used to attach a piece of electronic test equipment. T connectors were much used on co-axial 10M ethernet networks.

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