In some ways, you could consider the hub as similar to an audio/video distributor. However, contrary to audio/video one-way signals, a FireWire hub is like a network, with bi-directional signals. The standard defines FireWire as Peer-to-Peer connection; that is why two devices, or a device and a computer can talk to each other.
It is important to note that everything depends on your computer’s software, and the firmware of the devices. Sometimes, it is possible that a computer can work with many FireWire devices simultaneously (like a distribution), sometimes it can work with many devices in time-sharing mode (like a switcher). But most often it is possible to work one-to-one. In this case, you have to disconnect all the devices that are unnecessary at this time and leave only two of them. Since the FireWire is hot-plug standard, you can connect/disconnect devices at any time.
Hubs can be powered or unpowered. The FireWire standard lets devices draw their power from their FireWire connection. Obviously, a high-power device, like a professional DV camcorder, will have its own power supply, but low-power devices like a Webcam derive their power from the bus in order to simplify them. The power for this (up to 1.5 amps at 12 volts) comes from the computer.
If you have several self-powered devices, then your hub does not need to be powered, as none of the devices connecting to the hub needs additional power, and the hub itself can derive power from the computer. If you have many unpowered devices, you probably need a powered hub. The hub has to be powered from an AC adapter, which supplies power to the bus.
3.2 FireWire Compliance
In particular, the VS-4FW,VS-6FWand VS-8FW:
Fully support the provisions of the IEEE 1394-1995 Standard for High Performance Serial Bus and the P1394a Supplement
Are fully interoperable with FireWire™ and i.LINK™ implementation of IEEE Std 1394
Are fully compliant with OpenHCI requirements
Provide P1394a Fully Compliant Cable Ports at 100/200/400 Megabits per Second (Mbits/s)
Include full P1394a support, that is, Connection Debounce, Arbitrated Short Reset, Multispeed Concatenation, Arbitration Acceleration, Fly-By Concatenation, Port Disable/Suspend/Resume
Include Extended Resume Signaling for Compatibility with Legacy DV Devices
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