These are the Firewire cables with built in repeaters. It is possible to cluster them up to 49m (that's what it says on the box).
The problem is that it is not possible to directly connect them to the camera. Only a 4 Pin Male connects to the camera - not a large 6 Pin Male. So yet another cable is needed - which weakens the signal.
The perfect cable would be a 4 Pin Male to 6 Pin Male, 15m.
It exists as 10m - but is it supported by the hardware??

I don't think so. Mark gave me a very short adapter cable 4pin-6pin that i hooked up to the two 5m 6pin-6pin repeater cables - voilá it works. Thanks Mark!

The 4 Pin Male to 6 Pin Male Firewire cable:
http://www.lindy.com/uk/productfolder/03/30/30875/index.php
But does it repeat?? I thought that a firewire cable could not be longer then 5m.

One of these cables, of which i am using two, stopped working after only six weeks. Not very good quality. Trying to save money in these matters was a mistake. I ordered a firewire repeater now with independent power supply.