FireWire, also known as IEEE 1394, was designed to be a universal interconnect, eliminating the need for many different input/output connectors. The 1394 bus is a versatile, high speed, and inexpensive way to connect a wide variety of consumer electronic devices such as computers, digital camcorders, hard drives, scanners, printers, audio recorders, and videoconferencing cameras. With FireWire, it’s possible to connect up to 63 devices together. When 1394.1 bus bridges become available, it will be possible to connect over 60,000 devices together on a common bus.
There are currently two standards: the original FireWire, now referred to as FireWire 400 or IEEE 1394, and FireWire 800 or IEEE 1394b. As the names imply, the maximum speed of FireWire 400 is 400 Mbits per second, whereas FireWire 800 tops out at 800 Mbits per second. FireWire 800 is backwards-compatible, and unlike USB the FireWire bus speed is not diminished when a slower FireWire 400 device shares a FireWire 800 bus. The maximum cable length is currently 4.5 meters or around 15 feet.
There are three types of connectors associated with FireWire. The standard FireWire 400 connector for ports found on Macintoshes is a six-pin connector that looks like this:
Four of the connectors on the six-pin connector are used for the transmission of data, while the other two provide power to devices that are bus powered. FireWire can provide up to 45 watts of power through the connect, thereby eliminating the need for separate power supplies for peripheral devices.
Another popular FireWire 400 connector, found on devices such as camcorders and Windows PCs, is the 4-pin connector:
The four pins provide a data path to and from the device but not power.
Finally, there is the the 9-pin FireWire 800 connector:
Three of the pins provide power and the other six provide data channels for external devices.