Guide written by Falkra, whom I would like to thank once again for all her work on libellules.ch.
A visual tour of the sockets, connectors, cables and plugs commonly found in and around computers. If you're unfamiliar with it, it's not easy to find the name of a connector, or to search for it. The "flat, blue thing that plugs into the back" won't do much good under Google.
The names of data transmission protocols and connectors are often confused in common usage. When several names are used to designate a connector, details are provided. The name most commonly used in computing will be retained here as the main name.
Images have been taken from royalty-free or public domain image banks. I would like to thank their authors. For my part, I have taken a few photographs (prefix lib_), which can be distributed under a Creative Commons license (conditions of authorship and non-commercial use). To see the part devoted to interfaces inside the PC, go to this page.
USB
There are several types of plug :
Here's USB type A, the most common.
The smaller USB type B, often found on printers, scanners, etc.
And finally, mini USB (type A), often found on portable music players and cameras.
The left-hand grip is the most common form.
Developed name : Universal Serial Bus
Other names : without
Hot plug : usb can be hot-plugged.
Classic connection: universal, i.e. almost everything: keyboard, mouse, scanner, printer, external hard drive, joysticks, modems (prefer ethernet) and... usb flash drives...
Firewire
Two types of connector here, on the right the firewire mini (4 pins vs. 6 on the classic connector).
There are several bus speeds, the most common are 400 and 800mbps (there are more), here is the firewire 800 connector:
Developed name : without
Other names : IEEE 1394, iLink.
Hot plug : firewire can be hot-plugged.
Classic connection: external hard drive, camcorder
Ethernet (RJ45)
Ethernet is a protocol named after the connector (RJ45) itself.
Developed name : without
Other names: RJ45 (registered jack), 10baseT, IEEE 8802-3 and usually "LAN", ISDN, "network".
Classic connection: network...
RJ11
This is the connector used in fixed-line telephony.
This connector has 6 pins (2 usually used), as opposed to 8 for RJ-45, so be careful not to confuse them.
Developed name : registered jack 11.
Other names : "modem socket"...
Classic connection : telephone modem, fax, xDSL
BNC
This is a termination for a coaxial cable.
Male and female connectors.
A screen cable then a termination plug and "T". Developed name : Bayonet Neill-Concelman (from "baïonnette", because it locks).
Other names : 10base2.
Classic connection : network, screens.
DVI
There are several types of DVI connector, and not all carry the same signals.
Here's the DVI-D (D for digital). This connector transmits a digital signal only. It can be single-link or dual-link, depending on the amount of data transmitted. Dual link connectors send other RGB signals at the same time, for higher resolutions.
In comparison, the DVI-A (analog) port looks toothless. It transmits only an analog signal, and is simply a VGA port disguised as a DVI port, with the appropriate pinout.
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The DVI-I (integarted) port, which is very similar to DVI-D, only the pin usage is different. This is the most common port, with pins in absolutely every slot on the female plug, and it carries both digital and analog signals (one at a time, not all pins will be used, depending on the type of signal). No conversion is performed; it all depends on what you plug into it. Here again, dual link and single link.
For MAC, the ADC (apple display connector), a revamped DVI :
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Last but not least, mini-DVI for MACs, introduced for reasons of space. It can carry a digital or analog signal, and adapters to standard DVI, VGA or TV are often available. Four rows of connectors instead of the two of mini-VGA (see below).
The author requests an authorship link in the creative commons license, click on the image to access it.
Developed name : Digital Visual Interface
Other names : Digital Video Interface (obsolete).
Classic connection : monitors, digital or analog link.
VGA
The mini-VGA, for MAC, capable of carrying an S-video or composite signal. This connector was also launched to save space.
Developed name : Video Graphics Array
Other names : Video Graphics Adapter (inaccurate), D-SUB 15-pin.
Classic connection : monitors, analog link.
HDMI
This interface is digital and transmits audio and video signals. It will replace scart and s-video interfaces, and can be used for high-definition and multi-channel sound.
Developed name : High Definition Multimedia Interface
Other names : without
Classic connection : home cinema equipment, consoles, media centers, htdv, blu-ray players, DVD-HD.
Péritel
Away from the PC, but not necessarily far away, this connector is easy to identify !
On the right, a Peritel / 3 RCA & S-video adapter.
Developed name : peritélévision.
Other names : SCART (Syndicat des Constructeurs d'Appareils Radiorécepteurs et Téléviseurs).
Classic connection : TV, VCR, media center.
This connection carries analog audio and video signals.
S-Video
Both the name of the video connector itself and of the video signal separating luminance and chrominance.
Sometimes the connector may have more pins :
Developed name : separate video.
Other names : Y/C, DIN 4-pin.
Classic connection : TV output on graphics card.
Jack
A jack is a plug. There are several varieties, named according to their diameter. The most common are the following :
The 3.5 mm (1/8 inch) jack :
On the left, male and female. The one on the right is stereo, (number of sections).
The 6.3 mm (1/4 inch) jack :
On the right, the family (all called Jack...) : 2.5 mm mono, 3.5 mm mono and stereo, 6.3 mm stereo.
Name developed : audio jack.
Other names : without
Classic connections : audio (sound card, speakers (if not RCA), headphones, etc.).
RCA
Male and female connectors.
Developed name : Radio Corporation of America.
Other names : Cinch.
Classic connection : widely used for audio and video signals, to carry various types of digital or analog signals. A composite input/output (component) uses 3 RCA sockets, for example. Signals are analog, except in the case of SPDIF audio outputs, which are digital.
PS/2
Name developed : Personal System/2
Other names : Mini-din.
Classic connection : keyboard, mouse. Gradually abandoned in favor of USB.
PCMCIA
Found on laptops, these connectors accommodate expansion cards of all types (usb, wifi, ethernet ports, etc.). There are three types of PCMCIA card, distinguished by their thickness:
Type I: 3.3 mm
Type II: 5 mm
Type III: 10.5 mm
On the laptop side, open the small flaps to insert the card. On the right, the small eject button (push-button).
Developed name : Personal Computer Memory Card International Association
Other names : CardBus
Connection : expansion cards for laptops.
Parallel port
This connector takes its name from the data transmission mode.
Computer side :
Printer side :
Developed name : without
Other names : DB25, LPT (Line Printing Terminal)
Classic connection : printer. Obsolete, replaced by usb.
SCSI
This interface is faster and more complex than IDE; at one time, E-IDE and SCSI coexisted, the advantage of SCSI being its lower consumption of CPU resources than IDE. Controller cards took care of this work. There are 3 versions of the interface (SCSI-1, 2 and 3), with different transfer speeds as for IDE, E-IDE and UDMA.
Amiga, Apple and Sun used it, then IDE gradually replaced it.
This is where things get really complicated, depending on the type of interface and speed.
Here's a table, taken from Wikipedia (click to view).
SCSI-1, Fast SCSI and Fast-Wide SCSI (= SCSI-2) and ultra SCSI (SCSI-3 non wide) use this connector, a Centronics 50 (C50) :
But a DB25 or d-sub 25 connector (as for the parallel port) could be used, as shown below. This photo comes from my old scanner: to the left of the centronics 50 port (above) is this DB25 connector. The blue numbered module is used to define the ID (the identification number on the bus).
Let's complicate things a little. Since the centronics 50 connector is a bit large, a compact versino was released, the DH50, or high-density DB50, shown here on the back of a PCI card :
On the cable side, the male :
A rarer feature is a DB50 connector on three lines :
To transmit more data, more pins were needed for SCSI-3, a high-density 68-pin connector, here below the 50-pin :
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On a SCSI ribbon, this would look like this :
The author requests an authorship link in the creative commons license, click on the image to access it.
A VHDCI (ultra-high density) connector also existed in 68-pin for SCSI-3, in particular for RAID systems for hard disks :
Internal cables and connectors have the same appearance, and the number of pins and the shape of the connector are enough to identify them from the external connector.
On the Mac, a radically different HDI30 SCSI connector is available :
Name developed : Small computer System Interface.
Other names : "Skezi" (geek pronunciation) ;-)
Classic connections : hard disks, scanners, optical drives. Discontinued.
Series
This connector takes its name from the data transmission mode.
On the motherboard side, these are the two turquoise ports.
Developed name : without
Other names : DE-9, RS-232, V24.
Classic connection : 56k modems and various peripherals. Obsolete.
DIN
DIN refers to a family of connectors, in this case 5-pin DIN, used by older keyboards before PS/2 (and USB), but also for MIDI instruments.
Mini-DIN is used for S-video signals (4-pin), keyboards (6-pin, PS/2) and much more.
Name developed : Deutsches Institut für Normung (DIN).
Other names : XT/AT.
Classic connection : keyboards, MIDI equipment. Obsolete for keyboards.
Port JoyStick
Present on sound cards, this connector for joysticks and joysticks has now been abandoned in favor of USB. It could also be used for certain midi instrument connections (via an adapter), hence its presence on the sound card.
Developed name : without.
Other names : DA-15, game port, joystick port.
Classic connections : joystick, joypad, midi instruments.
Toslink
This is a connector for fiber-optic audio transmission. It emits a red light, and is usually protected by a cap or small removable panel. Rare on PCs (except sound card racks), but common on hi-fi systems and media centers, you'll find it more on the living-room side.
Not to be misleadingly referred to as S/PDIF (Sony/Philips Digital InterFace), as the latter standard uses a variety of connectors, including fiber optics via a TosLink link.
Name developed : TOShiba-LINK.
Other names : without
Classic connection : miniDisc, home appliances, media centers, DAT
Continuing with the connections inside the PC, go to this page.