The problem with that is that if there's a television in the home and children who are allowed to watch it, a conscientious parent soon realizes that there is little "safe" programming. Even networks whose programming is fairly innocuous make up for it by using trashy fillers in either the advertising or in plugs for other networks. And it's ridiculous to have sit there like a censorship sentry with a lightning quick finger on the mute button in an effort to control what the children hear. I know. I've done it. It gets to be almost comedic in itself...and disruptive to the continuity of the programming. Besides; it's likely that the constant bleeping or muting out of words, conversation or other inappropriate expressions will ultimately raise the level of curiosity the children have about such things.
Parental control devices are practically useless unless you block virtually all the channels...starting with the Cartoon Network. The only network I've ever had on in my home with children present that I felt fairly safe leaving on unattended for brief periods is Animal Planet. It would almost be better to only use the TV for prescreened movies, cartoons, etc. and avoid network programming and commercials altogether. Or just take the 
thing out of the house and spend the time reading books, playing games or sharing other quality time with them.