Public channels still need a digital de-converter box. All other channels must have a box from the provider that has a descrambler in it. They encode their signals so that you can't pirate it without a box.
Cable was (is in some parts of the world) analog in the US and used FDMs. FDM has bandwidth limitations resulting in a limited number of channels -- similar to how radio has a chunk of AM and FM frequencies to broadcast in.
With digital cable, the channels have increased dramatically, since there really isn't a frequency range limitation. The only requirement now is a high speed connection for uninterrupted signal transmissions. Television, phone, and internet all operate on their own frequencies on the line...similar to how DSL and telephones could co-exist. But with television, the box connects to the provider and requests the channel and the provider streams the video over, being decoded by the box.
Cable was (is in some parts of the world) analog in the US and used FDMs. FDM has bandwidth limitations resulting in a limited number of channels -- similar to how radio has a chunk of AM and FM frequencies to broadcast in.
With digital cable, the channels have increased dramatically, since there really isn't a frequency range limitation. The only requirement now is a high speed connection for uninterrupted signal transmissions. Television, phone, and internet all operate on their own frequencies on the line...similar to how DSL and telephones could co-exist. But with television, the box connects to the provider and requests the channel and the provider streams the video over, being decoded by the box.