In the era before satellite transmission, programming was transmitted by coaxial cable line, with the cooperation of the telephone company.

The cable had to be disconnected (dropped) at designated locations to allow the cars to coast by inertia, for example when crossing another cable line.

This function affords the cable company the ability to add or delete descrambling on the channels that come in through the coaxial cable line.

Microwave radio relay lines and buried cable lines were constructed to create a network of wideband carrier trunk lines, which covered the entire country.

Despite being shielded, interference can occur on coaxial cable lines.