Paul Doherty - PC Help – Firewire (IEEE 1394)

Connecting your PC to a camcorder

This is usually done with a "FireWire" lead, also known as an IEEE 1394 cable.

There are two standards 1394a and 1394b. Essentially 1394b is faster.

The 1394b standard is backwards compatible with 1394a – that is, a 1394b device will work with a 1394a device (but at 1394a speeds) providing suitable cables exist (see below).

IEEE 1394a

1394a devices have either of two sorts of connector – the 4-pin and the 6-pin. They are physically different and a 6-pin plug won't fit a 4-pin socket or vice versa. But the protocol is the same – if you connect a 6-pin device to a 4-pin device (with a suitable cable) they will work.

The reason for the two extra pins is that they carry power – so a 6-pin socket on a desktop PC, connected to a 6-pin socket on a camera (necessarily by a cable with 6-pin plug connected to a 6-pin plug), might provide the camera with power.

If the camera only has a 4-pin socket, the same PC could not provide it with power (so the camera would need its own battery or power supply) and they would necessarily be connected using a cable with 6-pin plug to 4-pin plug.

Of course, a PC (probably a laptop) might only have a 4-pin socket, because it's not offering power, and you'd need a cable with 4-pin plug to 4-pin plug to connect it to a 4-pin camera. Obviously power cannot be provided.

A camera with a 6-pin socket could be connected to a laptop with a 4-pin socket (using the same 4-pin to 6-pin cable mentioned two paragraphs above) but I can't imagine a camera would ever offer to power a PC, so – although it's technically possible – I doubt if power would flow.

IEEE 1394 is also called Firewire 400.

IEEE 1394a cables

There are three types (as we've seen above):
1. 4-pin plug to 4-pin plug.
2. 4-pin plug to 6-pin plug.
3. 6-pin plug to 6-pin plug.

IEEE 1394b

This uses a different connector again, a 9-pin connector. It includes power. Just as 4-pin plugs will not fit 6-pin sockets, so 9-pin plugs will not fit 4-pin or 6-pin sockets, and 4-pin and 6-pin plugs will not fit 9-pin sockets.

There are two sorts of 9-pin connectors: b-only or bilingual. They look very similar. (The b-only type has a slightly wider flange on its top.) A b-only plug will fit into a bilingual socket, but a bilingual plug will not fit into a b-only socket.

1394b with a bilingual socket is also called Firewire 800. (But I wouldn't trust retail vendors to get this right – I bet they call 1394b with a b-only socket "Firewire 800" as well, although technically they shouldn't. This is way beyond the average PC World assistant.)

A b-only socket indicates that the device can only speak to other 1394b devices. A bilingual socket indicates that the device is prepared to speak to 1394b devices and 1394a devices.

IEEE 1394b cables

There are three types:
1. Bilingual 9-pin plug to 4-pin plug.
2. Bilingual 9-pin plug to 6-pin plug.
3. B-only 9-pin plug to b-only 9-pin plug.

The last type (9-pin to 9-pin) can be used for connecting:
* bilingual socket to bilingual socket
* b-only socket to b-only socket
* b-only socket to bilingual socket.

You cannot get cables which have a 9-pin bilingual plug connected to a 9-pin bilingual plug. There's no point – if both ends are bilingual, they may as well speak 1394b to 1394b, and a b-only plug to b-only plug will do the job.

References

There's a very technical PowerPoint presentation (as a PDF) here; slides 17 and 18 have diagrams of the plugs, sockets, and cables.

A good Wikipedia overview is here, with pictures of the various plugs and sockets.