Cable service allows the transmission of large amounts of data over a single coaxial wire, including dozens or even hundreds of television channels as well as digital Internet communications. There are many ways to block a cable signal, however, and some service providers and even customers may take advantage of these technologies for various purposes. A cable TV block can strip out unwanted channels from a consumer’s lineup, prevent interference from their modem, or even block certain types of programming from young viewers.
The data transmitted through a coaxial cable line is similar to the signals transmitted through the air for broadcast television. The signal consists of data spread across a band of frequencies, with each “channel” transmitted inside a discrete frequency band. Unlike the broadcast spectrum, however, the signal through a coaxial cable is much more resistant to interference, allowing cable companies to broadcast more channels in a tighter frequency band without fear of signal degradation.
The simplest type of cable block is one that blocks out a specific range of frequencies. For instance, a company may designate one area of the spectrum for all its basic tier channels, another for expanded, and so on. By installing a filter that blocks the range covered by the expanded tier, an installer could prevent a customer from receiving those channels. Another use of these bulk frequency blocks is in the installation of a cable modem in a household without cable television service, as the installer can simply block out all the frequencies carrying channel information and leave the Internet connection intact.
The advent of digital cable has allowed companies a much finer control over channel blocking. With digital cable, the company digitally encrypts the signal before transmitting it across the coaxial network. The customer must have a programmed cable box from the provider to decrypt the information at all, removing the necessity for individual frequency blocks. Providers can program these boxes to allow or disallow channels at will, giving them a much finer control over service offerings.
Another type of cable TV block exists at the end user level. In their simplest form, these blocks can filter out entire channels, such as those that provide adult content. They may also allow users to block out channels at certain times of the day, in order to prevent TV watching during periods designated for homework or other activities. In digital cable setups, users can also block programs by rating, preventing children from seeing programming intended for more mature audiences.