Connectors (External)

This page will help you identify many common types of connector.

Summary

There are many types of connector, which can be confusing. This page will help you identify many of them, and in some cases, indicate whether a simple adapter will enable you to connect one type to another.

Safety

Always make sure that a connector is fully engaged. Never force it, and never pull it by the wire to unplug it.

Audio and Miscellaneous Connectors

Standard DIN

Five-pin male 180° DIN connector from a 1988 Schneider MF2 keyboard by Cherry

DIN connectors are primarily intended for analogue audio. The commonest are the 5-pin type which were often seen on cassette recorders when they were still much in use. The 5 pins were used for left and right, record and playback, plus ground return.

The same connector is still seen on digital musical instruments such as keyboards where they are used for MIDI. (Note that the MIDI lead marked Out goes into the socket marked In and the lead mark In into the socket marked Out.)

Different versions having from 3 to 8 pins are sometimes seen, occasionally as a power connector or for various other uses. DIN lounspeaker

Speaker DIN line socket (left) and plug (right)

A DIN loudspeaker connector is the same size but has just two pins, one of which is flat. This is sometimes used as a power connector on Christmas lights.

Mini-DIN

Color-coded PS/2 connection ports (purple for keyboards and green for mice) on the rear of a personal computer

This type of connector has been used for various purposes. Like the standard DIN, it comes in various configurations from 3 to 9 pins. In the 6 pin variant it's mostly remembered today as the standard PS/2 PC keyboard and mouse connector before USB became the norm. Early USB keyboards and mice often came with a USB to PS/2 adapter. These didn't convert USB to PS/2 - such keyboards simply sensed which protocol to talk by the voltages it sensed o the USB plug.

Older laptops sometimes had a 4-pin mini DIN socket for S-video output (see later).

Note that the pins in a mini-DIN connector are quite thin and easily bent. With care, they can be straightened but risk breaking off.

Phono

RCA or Phono plugs

Phono, or more correctly RCA connectors are commonly used for audio and video. For stereo audio there will be two, usually red and white. See later for video.

Adapters and Compatibility

Audio leads are available to connect two phono connectors to a stereo jack connector.

Video leads or adapter allow you to connect between VGA or SCART connectors and phono connectors.

Jack

Phone connectors:

• 2.5 mm mono (TS)
• 3.5 mm mono (TS)
• 3.5 mm stereo (TRS)
• 6.35 mm (1/4 in) stereo (TRS)

Jack (or phone) connectors have an ancestry going back well over 100 years, having first been designed for telephone systems. They have the great advantage that, being round, there is no correct or incorrect orientation in order to get them to mate, making it very quick and easy for a manual telephone switchboard operator to connect a caller.

Modern versions come in 3 sizes: standard 6.35mm (or 1/4"), 3.5mm miniature and 2.5mm sub-miniature, all used almost exclusively for audio, mainly headphones and microphones.

The simplest has just 2 conductors connected to the tip and the sleeve. These are designated TS. For stereo use a ring between the tip and the sleeve allows for a 3rd conductor, and these are designated TRS. The tip is normally the left channel and the ring is the right.

To allow for a microphone as well, there is a second ring, and these jacks are designated TRRS. Combined headphone and microphobe sockets are common on laptops, mobile phones and tablets, but unfortunately there are two different standards for how to connect the microphone, known as CTIA and OMTP.

PC microphones are generally TRS with the ring used to supply a bias voltage required by electret microphones.

TRRRS jacks exist but are unusual. The extra ring can be used for a second microphone or for supplying power.

3.5mm jacks are sometimes used for video, but beware: these may have a 17mm shaft which could damage a socket designed for the more usual 15mm jacks if forced in.

Adapters and Compatibility

Adapters are available for any of the three common sizes to any other, and in the various TS, TRS etc variants. If you want to connect a mono source to a stereo input or vice versa you'll need a correctly wired adapter (or make one up yourself). A headphone splitter allows two 3.5mm headphone jacks to share the output from one 3.5mm headphone socket.

If you need to connected headphones and a separate microphone to a combined socket you can get a suitable adapter with a TRRS plug on one end and two TRRS sockets one for the headphone and the other for he microphone, on the other. But there are two types: CTIA and OMTP. The specification for your laptop should tell you which you need.

You can also get male to male and female to female adapters, and adapters with a jack connector on one end and one or two phono connectors on the other.

XLR

XLR3 cable connectors female (left) and male

XLR connectors are very commonly used for better quality microphones, and audio connections more generally. For these applications they have 3 pins, though other variants exist. The 3 pins allow for balanced audio, that's to say, two of the pins carry the same audio signal but in opposite phase. At the receiving end the equipment doesn't respond to the absolute level of either, but the difference between the two. Any interference picked up along a cable run will be picked up equally in the same phase by both conductors and hence will be cancelled out by the receiving eqipment.

5-pin XLR connectors are used on DMX stage lighting control systems.

Adapters and Compatibility

XLR to jack and phono adapters are available in all possible combinations and genders.

Video Connectors

For a comprehensive list, see List of video connectors in Wikipedia.

Colour encoding

There are several ways of communicating an analogue colour video signal, using one or several separate wires and connector pins.

Component video uses three separate connections for the colour signal, and maybe two more for horizontal and vertical sync. The simplest to understand is RGB, where the red, green and blue signals are carried on separate connector pins. Horizontal and vertical sync signals may be carried on two more pins.

YPbPr is another component video scheme allowing easy compatibility with monochrome TVs and is hence use for analogue broadcast TV. Here, the Y carries the brightness (technical term: luminance), effectively the monochrome used by a black and white TV. Pb then carries the blue and Pr the red. If you subtract the blue and red from the brightness, all that's left has got to be just the green.

S-video, by contrast, carries the luminance combined with horizontal and vertical sync on one pin, and all the colour information (chrominance and saturation) cunningly combined on another. Audio is carried separately.

Composite video combines both of the S-video signals into a single channel, with some slight loss of quality. This is how analogue broadcast TV works. As with S-video, audio is carried separately.

Phono

Phono plugs (see above) may be used for analogue video. There may be a single yellow connector for composite video, or red, green and blue for component video, and perhaps yellow and white for horizontal and vertical sync.

SCART

A male SCART connector

SCART connectors (also known as Péritel, especially in France) have been around since video recorders first became affortable. It can carry analogue video as RGB, YPbPr or S-video and stereo sound. Some of those video formats can be carried in both directions (one at a time). In addition, it carries signalling, allowing a connected device to indicate that it's active. For example, this allows a video recorder to switch on a TV and display its output when the user presses Play.

Adapters and Compatibility

Adapters are available to convert video and audio output from a scart socket to phono sockets. It is also possible to convert a SCART output to VGA, though differences in the voltage levels used for the sync signals may mean an active coverter is required, containing minimal electronics.

Mini-DIN

Mini-DIN connectors (see above) in the 4-pin format may be used for S-video. These are quite often seen on older laptops.

Adapters and Compatibility

Adapters are available to convert S-video on a Mini DIN connector to composite video on a phono connector.

VGA

A VGA connector

A D-type connector with 15 pins in 3 rows has for many years been the standard video connector for attaching monitors and projectors to a PC or laptop.

This carries analogue video as separate RGB plus sync signals, as well as two digital pins (data and clock) which allow a display device to indicate to the video source (PC or laptop) the resolutions and refersh rates it supports, elinimating the need for manual configuration.

In recent years, VGA connectors have been increasingly replaced by HDMI, which is capable of higher quality.

Adapters and Compatibility

HDMI to VGA adapters are avaiable in order to connect a VGA projector or monitor to a laptop only supporting HDMI. (Note: since HDMI is also capable of supporting sound, a laptop may divert its audio output to the HDMI adapter, probably not what you want. Under SoundSetting on the laptop you should be able to select the speakers you want.)

If a long cable run is required between a computer and a projector (such as in a school church or public hall) then the signal may be degraded. Special adapters are avaliable to convert the signal to a form that can be carried over standard network cable using RJ45 connectors, over much greater distances and if required, to multiple display devices. The better ones require power in order to actively restore the signal at the receiving end.

Some older high quality monitors accept VGA input via 5 BNC connectors. You can get a cable with a standard VGA plug on one end and the 5 BNC plugs on the other.

HDMI

A standard HDMI connector

HDMI connectors are used for digital video and audio and are very common on modern audio-visual equiment and laptops, especially consumer laptops. They are largely superceding the older VGA type of connector, giving higher quality.

There are three sizes of connector: standard, mini and micro, 13.9, 10.42 and 5.83mm wide. All are very much the same shape and have the same number of pins. At a glance, the micro-HDMI connector could be mistaken for micro-USB, but is slightly narrower and fatter.

Like VGA, HDMI uses two of the pins for a data channel, which a display device can use to communicate its capabilities to the video source. This data channel can also be used for digital rights management.

Adapters an Compatibility

Adapters are readily avalable enabling all three sizes to be interconnected.

Passive adapters are available to connect a DVI-I or DVI-D source to HDMI display.

Although an HDMI alternate mode is defined for USB-C, no known products implement this, so it's not possible to connect a USB-C source to an HDMI display.

DVI

A DVI socket

DVI has several variants which can carry digital video (DVI-D), analogue video (DVI-A) or both (DVI-I).

The digital signals are carried on 24 pins in 3 rows. A lower bandwidth version has a block of 9 pins missing in the middle, and a dual channel version has 30 pins in 3 rows.

Analogue video is carried on 4 pins in a square plus a spade between them for ground return. These are not present in the photo, only a slot for the spade.

Adapters and Compatibility

The analogue signals in DVI-A and DVI-I are comptible with VGA, so a passive adapter can be used to convert between the two.

Similarly, the digital signals in DVI-D and DVI-I are compatible with HDMI with some limitations (protected content from an HDMI source can't be played on a DVI device) so passive adapters can be used to convert both ways.

DisplayPort

DisplayPort connector

Mini DisplayPort plug

DisplayPort is a highly versatile digital video and audio interface. The standard plug and socket are rectangular with with one corner bevelled. A mini version used on Apple computers is smaller and mor squat, with two corners bevelled.

Subject to support by the operating system, DisplayPort can drive multiple displays, daisy-chained together. This is achieved either with a DisplayPort hub or a DisplayPort output on (at least) the first display. This facility is known as Multi-Stream Transport, or MST. This is supported by Windows but not by MacOS as of macOS 10.15 ("Catalina").

DisplayPort can also carry a USB channel. Conversely, USB-C can carry DisplayPort signals, allowing a DisplayPort device to be driven from a USB-C source using a suitable cable, provided it's supported by the source.

DisplayPort cables come in different grades, a higher grade being required for higher resolutions and refresh rates.

Adapters and Compatibilty

DisplayPort Dual Mod (DP++) allows DisplayPort sources to use simple passive adapters to connect to HDMI or DVI displays. Such sources should bear a DP++ logo though many don't, in which case you'd need to consult the specifications.

RF

Aerial

BNC

F

Data Connectors

D-type: 9, 15 (2, 3 rows), 25, 37, 50 pin D-type

RJ45

RJ11

USB A, B, Mini, Micro, C

SATA

eSATA

PATA

Firewire

Thunderbolt

Lightning

Power Connectors

Laptop

General purpose round

Mains IEC, Clover-leaf, Figure-of-eight