Digital cable boxes like the Motorola DCT700 series are used by cable TV providers to provide customers with more features than can be offered over a coaxial cable connected directly to a TV. Cable providers typically purchase cable boxes from OEMs (original equipment manufacturers) but are provided to customers by the provider for either a monthly lease charge, or a single charge to own the cable box outright. In that instance, the cable box can be unlocked and used with any provider with which you contract for service.
Connect the coaxial cable from your wall cable outlet to the "RF In" connection on the back of the DCT700. Screw on the coaxial cable until it is hand-tight.
Attach either a second coaxial cable or a set of RCA cables from the DCT700 to the corresponding input on the TV.
Configure the TV to receive signal from the DCT700. If you used a coaxial cable, the TV should be changed to either channel 3 or 4; for RCA connections, the TV should be tuned to the video input into which you plugged the RCA cables using the "Input" or "Source" button on your TV's remote.
Contact your cable provider and have them send activation and authorization signals to your DCT700. Once the receiver has been activated, you have successfully unlocked it and can continue to use it with your new cable provider.