<Table> <Tr> <Td> </Td> <Td> The examples and perspective in this section deal primarily with the United States and do not represent a worldwide view of the subject . You may improve this article, discuss the issue on the talk page, or create a new article, as appropriate . (November 2017) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> The examples and perspective in this section deal primarily with the United States and do not represent a worldwide view of the subject . You may improve this article, discuss the issue on the talk page, or create a new article, as appropriate . (November 2017) (Learn how and when to remove this template message) </Td> </Tr> <P> Cable television signals are then mixed in accordance with the cable system's channel numbering scheme using a series of cable modulators (one for each channel), which is in turn fed into a frequency multiplexer or signal combiner . The mixed signals are sent into a broadband amplifier, then sent into the cable system by the trunk line and continuously re-amplified as needed . </P> <P> Modulators essentially take an input signal and attach it to a specific frequency . For example, in North America, NTSC standards dictate that CH2 is a 6 MHz wide channel with its luminance carrier at 55.25 MHz, so the modulator for channel 2 will impose the appropriate input signal on to the 55.25 MHz frequency to be received by any TV tuned to Channel 2 . </P>

The process of combining digital services in the headend is called