FireWire cable 800 9-pin connectors are part of a recent improvement to the IEEE-1394 technology, called FireWire 800 (or IEEE-1394b).
The improvement to the specification allows transfer of data at up to twice the speed of the original IEEE-1394 standard.
The 9-pin connector is a rectangle with square corners. It has 5 pin contacts on one side, and 4 pin contacts on the other.
This new connector type can be adapted to the older 4-pin and 6-pin connector. However, when adapted, the maximum transfer rate will be 400 Mbps.
This is an important cable if you have DV to Firewire Cable for Digital Camera, SLR, Machine Vision Camera etc