How handy is this photo? It sure makes a lot of prose unnecessary. These adapters cover just about any FireWire 400 or FireWire 800 conversion scenario one could think of.
Converter plugs for FireWire cables allow changing the cable plug type at the very end to match that of the port it's being plugged into. For FireWire 400 (IEEE 1394a) ports, there are converter plugs allowing 9-pin cables to plug into 6-pin ports and converter plugs allowing 6-pin cables to plug into 4-pin ports. For FireWire 800 (IEEE 1394b) there is an adapter plug allowing 6-pin cables to plug into 9-pin ports.