Cable television is an infrastructure that serves consumers as entertainment. It is a highly complex system in which information (television shows and movies) is generated at producing companies and sent through a series of components and middleware to reach consumer televisions. TV signals, both satellite and terrestrial, are sent to a processing facility called a headend. The signals are processed by the headend, distributed to trunk lines, and sent to homes by service drops (local electrical distribution lines). Then, the signal reaches a cable converter (cable box), which processes the digital signal and displays an image on a television.
Figure 1 shows the cable signal path from company to consumer. The significant middleware are the data encryption system, trunk lines, distribution amplifiers, service drops, splitters, and television sets. Trunklines are a convenient way of distributing the signal to many consumers. Instead of delivering the signal individually, they provide a single signal network that can be accesed by all consumers. Distribution amplifiers are used within trunklines to distribute the incoming signal to new outputs at the same signal strength. The carrying capacity of trunklines and strength of distribution amplifiers generally improves proportionately to the quality of a TV image. The transition to 3D cable television is important to consider for the future. Trunklines and distribution amplifiers are private middleware.
To prevent theft, cable television signals are protected by digital signal encryptions. Signal encryption is generally done at a headend and deciphered at local cable boxes. A cryptographic algorithm scrambles the signal into “cipher text” so that it can travel via an unsecured network. The strength of the encryption is dependent on a bit-sized value called a key. Additionally, there are different encryption companies. Encryption systems became common in the 1980, but have improved by increased translation speed and security. This form of middleware is in the private domain.
A service drop is an electrical line that runs from a utility pole to a house. Here, the cable signal is received from the trunklines and distributed to consumers. In some cases, the signal is passed through splitters so that cable signals can be received in different rooms of a house. The signal is proccesed by the cable converter, translated into readable information and displayed on the television. The service drop, and splitters are private middleware, and the television is public middleware. Televisions have drastically improved, while cable signal quality has leveled off in the past few years. The next major improvement to the cable infrastructure should be the transition into 3D tv distribution.
Figure 1- Cable Signal Path