Beginning Nov. 25, Cox Communications in Orange County will roll out a new technology that will change how viewers watch 100 channels. Most won’t notice a difference but a small number — less than 1 percent — won’t be able to see the channels at all. (Thanks to reader TiVoGirl for the tip.)

In a letter mailed to customers this week,  Cox said it is migrating to the Switched Digital Video platform, which is one way cable companies can offer customers more channels. This opens up space for Cox to offer more HD channels. I’ll get to those new channels in my next post. UPDATE: And here’s that post: “Cox adding 15 HD channels in December.”

Cox, like other cable providers, is operating at maximum channel capacity. It can only air a certain number of channels 24 hours a day. But some channels take up more room than others — one analog channel occupies the same space as about 12 to 15 digital channels. Switching those analog channels to digital is one way for cable companies to free up space. This is what Time Warner is doing (see story: Time Warner makes room for 100 HD channels, kicks out others“).

The other method is by moving to switched digital video, which converts channels to a type of on-demand-only service. Customers still use their remotes as normal, turning to the channel they want. The majority of customers won’t notice the change — only, I’m told, a slight delay when they turn to a switched channel. But customers who don’t have a set-top box and rely on CableCARDs won’t be able to access the channels. Alternatives for these users are below.

“Switched Digital will allow us to maximize our network capacity, enable increased HD channels and entertainment options in the future. For example, now we have over 400 HD programming options [hours] and we continue to launch more HD channels,” said Cox spokeswoman Lana Ong. (Corrected at 4:45 p.m. Ong says she meant to say 400 HD hours of programming is available.)

Here are the affected channels — 100 in all: Read the rest of this entry »