People who plug the cable directly into their TV are probably getting an analog signal. Those who use a box, be it a Charter-issued box or a Tivo-like system with a cable card, are using a digital system. People with newer digital cable-ready TVs, with a cable card, are also getting a digital signal.

Switching to digital lets Charter move more information through the same cable. The capacity taken by one analog channel equals 14 digital channels or three to four HD channels.

“It’s really a better service,” said Ian Olgeirson, media analyst at SNL Kagan, a securities and industry analytical firm. Switching does speed up broadband Internet service, which travels on the same cable, while giving TV viewers more options, he said.

The additional HD channels allow Charter to catch up with satellite TV systems and AT&T’s U-verse system, Olgeirson said. Charter’s Internet service is already superior to U-verse, and the switch should move Charter farther ahead, he said.

U-verse offers 190 HD channels, compared with 179 for Charter after the digital switch. Charter says it plans to increase the count to 200 later. AT&T says it plans to more than double its U-verse Internet speed by the end of 2015.