Lawmakers are turning up the heat on the NBC and BET networks to join the rest of the TV industry in using detailed ratings for sex, violence and bad language.

Rep. Edward Markey, D-Mass., and Senate Commerce Committee Chairman John McCain, R-Ariz., tried again to get NBC and BET on board Thursday, the same day the Federal Communications Commission approved the detailed ratings that ABC, CBS, Fox and major cable networks have been using voluntarily since October.NBC has stuck with a simpler ratings system previously used by the industry, and BET does not rate shows at all.

Markey and McCain, who helped broker a deal last year bringing about the more detailed ratings, sent letters to the chiefs of NBC and BET asking them to reconsider their positions. Six other lawmakers signed the letters.

The FCC on Thursday also approved "v-chip" technology that will let people block unwanted TV shows based on their ratings.

Markey said NBC and BET "are asserting their rights to plant a `bug' in the system. Just as a `bug' in a computer does not render the computer useless, the NBC/BET virus will not significantly harm the operation of the v-chip on every other channel. But it is a nuisance and a pain and is totally unnecessary."

NBC and BET are well within their legal rights to rate - or not rate - as they see fit because the rating system is voluntary. Both networks have cited constitutional concerns as the basis for their decisions.

An NBC official would not speak for attribution about the network's position on ratings, but, when allowed anonymity said viewers supported NBC's ratings.

"My sense is that we will stay the course," the official said.

BET spokeswoman Michele Moore would not say whether it was considering rating its shows. She would only say that "We're going to closely review actions at the FCC."

Vice President Al Gore, while not mentioning NBC or BET by name, also turned up the pressure on them: "There are still some networks who have yet to include the additional content ratings of S,V,L, and D. So I call on the holdout networks to join in one common voluntary ratings system so parents can have the V for their v-chips."

NBC does not use those letter notations, which flag sexual situations, violence, coarse language and suggestive dialogue. The rest of the TV industry adds one or more of those letters, when needed, to the age-based ratings of "TV-PG," TV-14" and "TV-MA." NBC uses only age-based ratings - from "TV-G" to "TV-MA."

Consequently, were a person to block out, for instance, only shows carrying the "V" notation, none of NBC's programs or any unrated programs that may contain violence would be blocked out, regulators said.