The CDM-630 is an interesting yet unpopular device.
In hardware, it converts PAL to NTSC, and NTSC to PAL.
And then it will pass NTSC to NTSC and PAL to PAL.
As far as the TBC goes, there's a catch. It ONLY works on conversion, not passing native. So it cannot be used a general TBC. It's a direct pass, bypassing the TBC altogether. I've seen devices like this before. It's sort of like how S-VHS VCRs combine DNR with TBC, and you cannot shut off the DNR. Here it's paired with signal conversion, or not at all.
If you want a conversion box, I've see worse. It's mostly good for lazy conversion, where you don't want to mess with the quality software conversion methods (Avisynth, audio editors for 4% adjustment, etc).