What does a TBC do?

[amiman99]

TBCs correct and synchronize the video source to each other.
Video Toaster NEEDs them to operate correctly.
Very easy to use, just video IN, video OUT, sync.
Video Toaster manual shows you how to connect them correctly.

BTW, you can use the TBC to strip the Macro-vision from DVDs and VHS.

[amiman99]

When you have a Video Toaster and you want to do any wipes from one source to another then you NEED at least one if the first input is from video camera, if your inputs are from VCRs then you need 2 TBCs.
VHS signal is not stable at all, you need to fix it before using in the Video Toaster.

[amiman99]

You don't need one under all circumstances. Their main function back in the day was to correct the unstable analog video signal output by VCRs. Live cameras and digital video sources (DVD players, DV cameras) don't need them, for instance.

Although I think if you have more than one input source, regardless of whether it's digital or not, you do need one (or two?). That was never really clear to me, since the manuals all pre-date the digital formats.

If your source is camera with stable input you dont need one, in this situation you could use Toaster as a genlock.
When you have 2 sources and one of them is stable you can use one TBC, just connect stable input to Genlock IN and other to Video IN.