ramborums

Are there some types of cameras which cause drop in brightness when used with DVR cards? I have 4 types of cameras connected. Two of them work fine, whereas 2 others start with normal brightness when switched on, then fade off to a very dark level. This fading off does not happen when connected to AV of TV. The ones which are working i think are sony and the ones which have a problem are cheap, some brand called CGH, 805D. I got them cos they are just unimportant additions. Are there any specific specs to look for in getting cameras for a DVR card? The card type is connexant. Any inputs what could be the problem? Thanks

I have setup a DVR card with PICO2000 DSR. When I connect each card one at a time, the brightness level is good. But when I connect more than one at the same time, the camera display goes very dark. How and why is this change in brightness happening. Is there any setting that can control this? If possible, individually for each camera. I am using small security camera I got from ebay. Thanks