There are several kinds of cables you can use with your computer. Each cable type can be used for different purposes. To use a cable, your computer must have a port for that cable. Some computers have all kinds of cable ports, other computers only have the basic cable ports. It may be important to know which ports your computer has.

The part of the cable you plug into devices is called a connector (sometimes also a "jack" or a "plug").

In review:

• A cable is the actual wire that connects two devices
• Connectors are at both ends of a cable
• Devices have ports which connectors fit into

Keep in mind that most cables have "mini" connector versions, so they can plug into smaller devices.

There are several categories of cables, including:

• Peripheral cables: used to connect computers to external devices like printers, mice, hard drives, etc.
• Audio/Video cables: used to connect computers to computer monitors, TVs, microphones and speakers
• Network cables: used to connect 2 or more computers together in a network
• Legacy cables: old cables which are not used much any more

Peripheral Cables

Name	Symbol	Image	Other names	Versions
USB			Hi-speed USB (2.0), Superspeed USB (3.0)	USB 1.0 was released in 1996, with 1.1 coming in 1998. Both versions were slow, with speeds from 1.5 Mpbs to 12 Mpbs (up to 1.5 MB/sec). These were so slow that they were mostly just good for mice, keyboards, and printers. The slow speed allowed Firewire to become somewhat popular.
				USB 2.0 was released in 2000, but was not available on many computers until 2003. With a top speed of 480 Mbps (60 MB/sec), it finally allowed an alternative to Firewire, and now most computers use USB, with Firewire mostly left serving specific professional markets.
				USB 3.0 will be released in 2010, with a reported speed of 4.8 Gbps (600 MB/sec). It will also allow for more power to be transmitted, allowing for faster battery charging (current USB is weak in that regard).
Firewire			IEEE 1394, iLink	Firewire was first released in 1995 with a speed of 400 Mbps, able to transfer up to 50 MB per second. Because USB 1 was so slow, FireWire was used for most situations where speed was necessary, like video transfer, DVD recorders, or hard disk drives. Firewire is called "iLink" when used in video cameras.
				Firewire "b" (also called Firewire 800) was released in 2002 with a speed of 800 Mbps (100 MB/sec). It had a different connector, so was not compatible with the original Firewire. It is mostly used by professionals.
				Firewire S1600 and S3200, released in 2008, have speeds of 1.6 Gbps and 3.2 Gbps (200 and 400 MB/sec). They have the same connectors as Firewire b.

Firewire 400 and USB 1.1 both came out in the late 1990's. At that time, USB was only fast enough for devices like mice, keyboards, and printers. Firewire was about 40x faster, and so was used for external hard drives, optical drives, and video transfer.

For the first five years when USB 1.0 and 1.1 were used, Firewire should have been the clear winner in the "cable wars." However, USB was supported by Intel and Microsoft, who controlled most computers made, so despite its weak abilities, USB remeained the #1 cable choice. Additionally, Apple (which created Firewire) asked for too high a price for using Firewire, which discouraged computer makers from using it.

A few years ago, both types were upgraded. USB 2.0 was released, and the speed was about the same as Firewire 400. Today, USB 2.0 is quickly becoming the standard cable for most devices, though many devices can use both USB 2 and Firewire.

Firewire 800 was also released. It is about twice as fast as USB 2 and Firewire 400, but most people don't need such high speeds. Firewire 800 is used mostly by people with special high-speed data transfer needs.

More images can be found below.

Audio/Video Cables

Video cables are the important point here. There are two basic types:

• cables to connect to a computer monitor or an HDTV
• cables to connect to a TV set (non-HDTV)

For connection a computer to a computer monitor or an HDTV, you can use HDMI, DisplayPort, VGA, or DVI cables.
F or connecting a computer to an old-style TV, you can use RCA or S-Video cables.

Type	Name	Connector	Port	Description
Video: connect to a monitor/ HDTV	HDMI			A new, high-speed video connector used with HDTVs. Recently, computers have included these. Has built-in DRM copy-protection. Carries audio and video.
	DisplayPort			Similar to HDMI, it can carry audio and video and has DRM copy protection. However, DisplayPort is cheaper.
	DVI			Digital connector, designed for better use with LCD monitors. It is capable of carrying an audio signal, but usually does not.
	VGA			Most common video monitor cable/port used for computers. Designed for CRTs, but can be used with LCDs. Carries video only.
Video: connect to a TV	RCA			Audio/Video combination. Yellow is video, red is right-audio, white is left-audio.
	S-Video			Video only (no audio). This is most common type of TV-out port on computers.
Audio	Audio			Used for mono/stereo audio. Most computers use this jack.

Right now we are in a transition, from old analog "NTSC" TVs to higher-resolution HDTVs. The old RCA and S-Video cables will disappear over time as old TV sets are discarded.

You should become familiar with what cable ports are on your computer. Depending on what ports your computer has, you can connect with a variety of displays and TVs. The ports will also tell you what kind of cables you will need to buy.

Many times, your computer's ports will not match the ports on a cable or TV. Usually, this can be fixed with an adaptor--a cable which has one type of connector at one end, and a different type of connector at the other end. For example, there are cables which have an HDMI port on one end, and a DisplayPort connector on the other, as seen below.

Network Cables

Computers can be connected in a LAN in two ways: with or without wires. Without wires is called "WiFi" (see next page). With wires is called "Ethernet."

Ethernet cables are very similar to normal telephone cables, except they have 8 wires inside instead of 4. Ethernet cables are also called LAN cables or Network cables. Below are images of Ethernet cables (at left), and telephone cables (at right) for comparison.

Ethernet		Telephone (not LAN)
connector	port	connector	port

Each computer has one Ethernet port. Two computers can be connected directly, with only a cable. Three or more computers require a hub to be used.

Using a hub is very simple. Just connect the computers to the hub with Ethernet cables; the rest is automatic.

Hubs are very useful for computer labs, or for connecting all the computers in entire buildings. Here is a layout of the computer network at the old LCJ building:

The diagram at left shows the old LCJ network in rough detail. The red objects belong to the student network, and the blue objects belong to the office network. The big squares on the 2nd floor are the servers, or "boss" computers of each network. The circles are computers; triangles are printers; and green diamonds are Ethernet hubs. All the objects of the same color can communicate with each other. For example, a computer on the 1st floor could open a document saved on the server on the 2nd floor, then print it out on a printer on the 8th floor. The servers, in turn, are connected to high-speed fiber optic cables (not shown) connected to the Internet.

All the cables joining these computers are Ethernet cables.

Legacy Cables & Ports

"Legacy" cables are older cables and ports which are not used much any more. These include Serial, Parallel, and SCSI cables and ports.

Serial and parallel cables were too slow to keep. Parallel and SCSI cables were big and heavy. And all three cables were not "hot-swappable."

What is "hot swap"? Today, USB and Firewire cables can be connected and unplugged at any time, without turning off the computer; this is called "hot swapping." Legacy cables were not hot-swappable, which means that every time you wanted to plug something in or unplug something, you had to turn off the computer, do the plugging, and then turn the computer back on again. That was very inconvenient.

You will see serial and parallel ports on the back of most Windows computers; they are kept to help people with old equipment. However, they are disappearing as time goes on. Macintosh computers removed all legacy ports more than 6 years ago.

Serial	Parallel	SCSI

Depending on what you want to do with your computer, the various ports may or may not be necessary for you. Check the computer you will buy to see what ports it has!

REFERENCE CHART (see the cable chart in your classroom for a better look):

	ports	cable connectors
USB
Firewire (also called IEEE 1394 and "iLink")
Network (Ethernet)
Network (Telephone)
Audio In and Out
Monitor/HDTV (VGA)
Monitor (DVI)
Monitor/HDTV (HDMI)
Monitor (DisplayPort)
TV (S-Video)
TV (RCA)