Final answer:
Cable networks transmit several channels by using multiplexing, which is the combining of multiple signals over a single medium like coaxial or fiber optic cables, often without the need for local station affiliates.
Step-by-step explanation:
Cable networks that can transmit several channels from one network engage in multiplexing. Multiplexing is a method where multiple analog or digital signals are combined into one signal over a shared medium. In the context of cable television, this allows for the transmission of multiple television channels over a single cable system. It contrasts with the traditional model where local stations broadcast network programming through the airwaves.
A local station that broadcasts national network programming is known as an affiliate. Cable networks, however, often operate without local affiliates because they transmit programming through coaxial or fiber optic cables directly to homes, bypassing the need for aerial broadcast. This direct approach has led to the rise of specialized channels that target specific audiences, thereby altering the landscape of television advertising and content distribution.