A box for the television?

You're talking Set-Top-Box, which is a cable box. It is generally placed in customer's house and it works by receiving commands from the cable company. Such commands decode a particular channel and so the customer gets to watch only the channel that he subscribed to. It depends whether those local channels are actually pay-per view channels or free-to-air channels. Pay-per view channels are generally digitally encrypted while sending signals to the set-top-box and so, only the subscribers are able to decode those signals at their home with that box and watch those channels. On the other hand, free-to-air channels usually are not encrypted and they can be viewed by any one thus, with or without the box, with or without the subscription (there's no need to subscribe actually). Hope it helps. :)