I've used mine with Moto cable boxes DCT2000, DCT2500 & DCP501.
They use either a DB9 or 1/8" phone plug depending on the STB.
The trick is that some cablecos (Shaw for sure) uses a DCT template that does NOT enable the needed hi-speed data port.
If yours does, then you are golden.
I've also used them as 1080i upconverters for my DVD or VHS player, very cool.
Now taking offers on mine... Do I hear a bid...