You would typically plug the bullet camera into an A/V IN socket in the device you're recording to. In this way your expensive camera/video recorder can sit in a waterproof tank bag/rucksack/pocket with only the bullet camera and the leads running to it, being exposed to the elements.
That's definitely the case with my set-up. My bullet-cam (which is about the size of a lipstick) has something like a 6ft cable that needs to be plugged into an analogue A/V in on the camcorder - so effectively the camcorder just acts as a video-recorder. Apparently having an A/V in puts the camcorder in a different duty bracket, which is why it's a reasonably rare feature in the UK.
I use a Canon MV700i which has a knackered CCD so it's no use for anything else anyway, but works fine for this. My Deauville had a compartment in the fairing that the camera and associated gubbins (cables and bullet-cam power-supply) fitted in, but on the other bikes I use a tankbag.
If you want to give it a try sometime then you're welcome to borrow the set-up, including the camcorder. On a thumper it'd probably work better as a helmet-cam, because of the vibes when bike-mounted, but it's not something I'm keen on myself as the speedo reading might then get included...
