PC Sockets and Cables

Without any ports or sockets a computer wouldn’t be much use ­ you couldn’t easily connect a monitor, keyboard or mouse. Today, though, just about every desktop and laptop is covered in sockets, with many different types doing much the same thing. And, annoyingly, they’re usually not labelled at all.

Here, we have produced a complete pictorial guide to every socket you are likely to find on a modern, or even not so modern, computer.

So the next time you find yourself wondering exactly what on earth that strange square socket on the left of a laptop is there for, or which one of the three alternatives is the best way to connect an external disk, you’ll find the answer here.

1
In this picture, the left-hand socket is for connecting to a wired network. There are three speeds of network: 10Mbits/sec, 100Mbits/sec and 1,000Mbits/sec, known as Gigabit Ethernet, but all use an identical-looking socket. Most modern computers have a 100Mbits/sec socket. Many sockets include two small flashing lights to show when the connection is active. The socket on the right is Firewire 800, a newer, faster version of Firewire. Unlike USB2 and USB1 the two use different connectors. Firewire 800 is an extremely fast way to transfer information between a PC and external device such as a hard disk, but it’s relatively rare on Windows PCs.


2
On the left is the Mini DVI connection. This carries the same information as DVI (see step 9) and can be converted to a DVI socket using an adapter. It is rare and found only on Apple Mac computers such as this Mac Mini. The Mini DisplayPort, on the right in this picture, is a small video connector that can be found on some desktop and laptops, primarily those made by Apple, and a few projectors. Adapters are available to convert Mini DisplayPort outputs to a DVI-D connector.


3
USB (Universal Serial Bus) sockets such as this pair of USB 2 Type A can be used to connect just about any peripheral device, from printers to cameras, to scanners and hard disks. Most use the USB2 standard, but older PCs may have the slower but identical-looking USB1 ports. USB can work with many types of socket and plug: this Type A socket is the most common on PCs, but the squarer Type B socket is often found on printers and smaller Mini-B sockets are common on cameras (see step 13). All are interchangeable, so a cable can have a Type A plug on one end and a Type B plug on the other, for example.


4
The PS/2 connector is used to attach a mouse or keyboard. Many come in pairs, with a green connector for a mouse and a purple one for the keyboard, but this port can accept either. Although most mice and keyboards now connect via USB instead, many desktop computers continue to include these sockets for older peripherals. They can be handy: some PCs have Bios setup tools that can only be controlled via PS/2, and as most USB mice and keyboards include PS/2 adapters they can be used to free up a USB port for other devices. The abbreviation means ‘personal system 2’.


5
On the left is a Co-axial S/PDIF. Like the optical S/PDIF socket (see below) this connector is used to transmit digital audio to an external decoder. Unlike the optical version, however, it uses a standard RCA phono cable. On the right is an Optical S/PDIF socket. One of the silliest acronyms in computing, S/PDIF stands for Sony/Philips Digital Interconnect Format and is a way to transmit sound digitally. It’s also a method for transmitting information rather than a connector, so there are two common types of S/PDIF socket: optical and coaxial. This optical type, sometimes labelled TOSLINK, must be connected using a special fibre-optic cable. S/PDIF is used to link a computer to an external surround sound decoder, and as such is only of use to serious audio or home-cinema fans.


6
On the left is the eSata socket. The Serial ATA (Sata) system is used to connect the hard disks inside most modern computers, and eSata is a version of that system designed for external disks. Because most external hard disks contain a Sata hard disk inside, eSata allows for a direct link between the computer motherboard and the disk without any need for a system such as USB or Firewire. ESata allows for very fast file transfers, but it is still relatively uncommon and set to be superseded by USB3. On the right is a Firewire 400 port. Like USB, Firewire can be used to link many types of device, but it is most common on external hard disks and camcorders. This six-circuit connector is most common on desktop PCs, while some laptops have a smaller four-circuit Firewire socket. Firewire is also known as I.Link (on Sony products) and by its technical name IEEE 1394, so you may see either labelon the socket.


7
Most PCs use 3.5mm audio sockets that accept a jack plug of the type commonly found on portable headphones. These are usually colour coded: green for stereo audio output and pink for mono microphone input. Some PCs include extra surround-sound channels coded black (stereo rear speakers) grey (stereo side speakers) and gold (centre speaker and subwoofer). Some include a blue socket, which is a line-level stereo audio input.


8
The HDMI (High Definition Multimedia Interface) socket provides a digital video picture and sound, so there is no need to use an extra audio cable alongside an HDMI one. HDMI inputs are common on high-definition televisions, and outputs are becoming more common on computers. HDMI has a lot in common with DVI (see step 9), so the two can be linked using an adapter to transmit video but not sound.


9
The VGA port is correctly known as a D-Sub DE15 socket, but everyone knows it as VGA (Video Graphics Array). It’s used to connect most older computer monitors, and is found on many older desktop and laptop computers as well as some flat-panel TVs. It supports only an analogue video signal, so when possible a DVI or HDMI socket should be used instead.


10
The white DVI or Digital Video Interface white socket for displays has replaced the older D-Sub VGA socket on most desktop and laptop computers, and can also be found on some flat-panel televisions. Most DVI outputs (marked DVI or DVI-I) can transfer both digital and analogue video, so it’s possible to connect a VGA monitor to one using a small adapter, but those marked DVI-D cannot be used this way. An alternative Mini-DVI socket is found on some Apple computers; this can be converted to DVI using an adapter (see step 2).


11
The yellow Composite Video plug at the bottom of this picture is found on some PCs. It carries a low-quality video signal. It can be converted to a Scart plug using an inexpensive adapter. Sound must be carried separately; normally using a stereo phono cable. The Component Video socket (at the top of the picture) is a high-quality video output that is sometimes available on powerful graphics cards using an adapter. It uses three RCA phono plugs, coloured green, red and blue, and is sometimes labelled YPbPr. It is capable of transferring high-definition video, but separate audio cables are required.


12
USB Type A is the most common type of USB connector. It has a flat rectangular plug. Almost every common peripheral will use one of these to connect to your PC.


13
USB Type B connectors are generally used to connect printers and scanners. This end will go into the printer, with a USB Type A plug (see step 11) on the other end for the PC.


14
Although there are many types of small USB connector, the USB Mini B is most common. It's often used to connect cameras and music players, with a Type A plug (see page 11) on the other end for your PC.


15
The Ethernet cable is used to make a wired network connection. You might connect one between your PC and router, for example.


16
A Firewire 400 cable of this kind is normally used to connect a camcorder to your PC, although some modern camcorders use USB instead.


17
The circular PS2 connector might be found on an older mouse or keyboard. Look for a green (mouse) or purple (keyboard) socket on your PC.


18
The VGA plug connects an analogue monitor to your computer. If no suitable socket is available you may need a DVI to VGA adapter.


19
The DVI plug, normally coloured white, connects a monitor to your computer. Look for a white socket on your graphics card or laptop.