Computer screen wiring

There are several ways of hooking a screen up to your computer - sometimes its useful to know what system yours is using. This page will help you work out which you have. Its common for modern computers to have at least two and quite possibly more of the connectors shown here. You will need to use one which is supported by both the computer and the screen. In many cases its also possible to use more than one at a time, providing dual screens on a single computer. This can be used either to replicate your screen to make the display visible to more people, or to spread your computers display over multiple screens to give you more on screen work space.

VGA carries analogue video and no sound. It will give a slightly less sharp image than the other digital connections shown on this page, but it is commonly available.

The matching VGA plug - normally the lead will have the same plug at both ends, and the computer and the screen will have sockets fixed to them.

VGA

VGA is the oldest type of connection still used - its supported by most PCs and many screens. It carries analogue video. The socket is in a D shape, with 15 pins in a 3 row configuration. They are often coloured blue.

VGA connectors normally have screw posts on the plug, these allow it to be screwed into the socket so that the lead will not work lose or pull out.

Interoperability

VGA sockets can normally only connect to screens with VGA inputs. (while its possible to convert VGA to and from other video formats, it takes a more expensive powered adaptor to do this and not just a simple cable or plug in adaptor)

Sound

VGA does not carry sound, you will need a separate sound lead to carry sound to the screen.

DVI

This is an example of a DVI-D connector - the digital only version. The version that can carry analogue video has an extra couple of connections above and below the wider slotted connection at the right hand end.

DVI is multi standard interface that can carry both analogue and digital video, although the exact capabilities depend on the exact type fitted. Not all types carry analogue video for example. The plug normally is fitted with thumb screws to fix it in place.

It is usually used to carry digital video.

Interoperability

DVI can usually feed DVI, HDMI, and Display port inputs on screens when equipped with the correct cable or adaptor. DVI to DVI and DVI to HDMI being the most commonly used.

Some DVI ports can also drive a VGA screen. (these can be recognised by the additional two connections above and below the wide slotted pin at the end of the connector).

Sound

DVI does not carry sound, you will need a separate sound lead to carry sound to the screen.

The matching DVI lead normally with the same plug at both ends. Note that they are not always white - many are black.

HDMI

This is an example of a typical HDMI socket. The computer end will normally be marked as an "out" or output connector, and the screen may be marked with "in" or input. Note that some screens also have more than one connection to allow them to display a picture from more than one computer or device.

HDMI is a modern video and audio interface found on lots of computer equipment and also all modern TV and AV equipment. HDMI leads are not normally latching and just rely on friction to keep them in the socket. This makes them rather easy to pull out by accident.

This is a typical HDMI lead. Usually with the same plug on both ends. Leads are available in quite long lengths as well.

Interoperability

HDMI can usually feed DVI, HDMI, and Display port inputs on screens when equipped with the correct cable or adaptor. HDMI to HDMI and HDMI to DVI being the most commonly used.

DVI ports can't drive a VGA screen without a more expensive electronic adaptor or converter.

Sound

DVI carries sound (in fact full surround sound) but only when connected to another HDMI input or a Displayport input.

Note that when a computer is connected via HDMI to a screen that has speakers, the sound output of the screen will appear to the computer as a completely separate sound output to the computers built in analogue sound capabilities. So you may need to explicitly switch the computer between its analogue audio and the screens HDMI digital audio when plugging in headphones for example.

Displayport

A Displayport connector - note the square corner on one side of the socket - this will prevent a HDMI lead being inserted by mistake.

Displayport is one of the latest digital video standards used on computers. At a glance it looks very similar to HDMI, but the connectors are asymmetric - having one square corner and one bevelled one, unlike HDMI which is bevelled on both sides.

This is a matching Display port plug. WARNING Many display port plugs are "latching" connectors. If you look closely at the picture above you will see there is a button on the top of the plug, and two small metal barbs that point up from the top of the connector. When the connector is inserted into the socket, the barbs will lock it into the socket, and you must push the button on the plug to be able to withdraw it from the socket. If you attempt to pull it from the socket without pressing the button, you may end up damaging the lead, or the socket or both!

Interoperability

Displayport can usually feed DVI, HDMI, and Display port inputs on screens when equipped with the correct cable or adaptor. Displayport to HDMI and Displayport to to DVI being the most commonly used.

Displayport can't drive a VGA screen without a more expensive electronic adaptor or converter.

Sound

Displayport carries sound (in fact full surround sound) but only when connected to another HDMI input or a Displayport input.

Note that when a computer is connected via Displayport to a screen that has speakers, the sound output of the screen will appear to the computer as a completely separate sound output to the computers built in analogue sound capabilities. So you may need to explicitly switch the computer between its analogue audio and the screens digital audio when plugging in headphones for example.

USB with Thunderbolt

A USB-C style port that also has a thunderbolt capability and so can drive a screen as well as other USB devices. Note that the connector is identical to a normal USB-C connector, however you have find additional symbol printed near it that indicate you can connect a screen.

This is a USB-C to HDMI adaptor. Similar devices exist for HDMI, and DVI screen inputs.

Very modern desktop machines and many laptops (including Macbooks and Chromebooks) may have a USB C port that also supports thunderbolt devices. This enables USB to drive a video display as well as more common USB devices. Unless you have a screen with similar USB-C port that will allow a direct connection with a good quality USB lead, you may need an adaptor ro convert to HDMI, DVI, or DisplayPort.

Interoperability

USB-C / Thunderbolt can drive a USB-C screen directly, or can usually feed DVI, HDMI, and Display port inputs on screens when equipped with the correct cable or adaptor. USB-C to HDMI and Displayport being the most commonly used.

USB-C can't drive a VGA screen without a more expensive electronic adaptor or converter.

Sound

USB-C carries sound (in fact full surround sound) when connected to a USB-C, HDMI, or Displayport input.

Note that when a computer is connected via USB-C to a screen that has speakers, the sound output of the screen will appear to the computer as a completely separate sound output to the computers built in analogue sound capabilities. So you may need to explicitly switch the computer between its analogue audio and the screens digital audio when plugging in headphones for example.

Audio Connections

Most computers also have analogue audio connections that allow the computer to be connected to speakers, headphones, microphones etc.

Analogue Audio

Modern machine also support additional speaker connections to support full surround sound. These typically all use the same 3.5mm mini jack connector (like that found on most headphones), and usually the speaker one is coloured green.

USB Sound

Some sound devices may connect via USB, for example a USB headset with microphone and headphones, or a USB web cam with camera and microphone. The USB sound device will appear as a separate component to the analogue sound it has built in, so in some cases you may need to manually switch which you are using.

Solving sound playback problems

Sometimes you may find that you are unable to hear the sounds produced by your computer. This section will help identify the cause of the problem.

Sound not supported by screen

Many screens have built in speakers, and should provide sound. However there are a few than may not have speakers. Normally screens with speakers will have buttons on the front for adjusting the volume level. If you can't see these, then look at the identification plate on the back of the screen, and search for the make and model of screen on google. This will usually identify if the screen has speakers. (often screens with sounds may be described as "multimedia").

Missing sound lead

If you screen has speakers, check whether you need a separate sound cable (see above), and if you have one fitted. Note you will only need a separate sound cable if you screen is connected by VGA or DVI (see above).

Volume too low on Screen

Check the volume is turned up on the screen. This is normally available on a pair of "up" and "down" buttons, but may only be available via an on screen menu accessed from a button on the screen.

Note that laptop screens don't have separate volume controls - the volume is controlled only from the computer.

Volume too low or muted on Computer

The speaker Icon on Windows 10

Windows master volume control

Check the task bar near the clock - there is typically a speaker icon. If you click on this you should be able to set the output volume from the computer or mute the sound altogether. If you can't see the speaker, then click the small up arrow near the clock to display any "hidden" icons.

Note that on laptops, the volume is normally adjusted with a combination of key presses. Usually you hold down the special "Fn" key on the bottom line of the keyboard, and tap either one of the number keys or the functions keys. Look for the keys with the speaker icon printed next to them.

Wrong audio device selected

You can change change the selected sound device from here

When a computer has multiple sound output devices (say its built in analogue sound, and a sound capability on a screen connected via a HDMI lead). You may need to switch to the correct device. To do this, click on the speaker icon with the right mouse button, and select "playback devices". Now click on the device you want form the list, and the "set default" button.

The windows sound control panel will let you choose your sound device, and also test your sound system. (click for larger version)

Headphones plugged in

When you plug in headphones, the computer may mute the speaker output. You will need to unplug them to hear the speakers. (or in many cases you can change the auto muting of the speakers from control panel - but this can get complicated!)