The silence of Web radio is about to end. A deal announced late last month promises to bring hundreds of radio-station streams back online this summer.

Clear Channel Communications, which operates about 1,200 stations in the United States, has signed with Hiwire, a Los Angeles-based ad-insertion company, to replace "terrestrial" ads with commercials targeted specifically at Internet audiences.

In mid-April, Clear Channel and other radio broadcasters yanked their content offline, citing the fee – $220 for 13 weeks – that the American Federation of Television and Radio Artists requires them to pay ad agencies to compensate union actors and announcers who perform in ads. Clear Channel said it wouldn't bring back its Internet streams until it made "legal and financial sense" to do so. Apparently it does now.

The union's Web contract requires only a $660-per-year fee. About a fifth of Clear Channel's stations are scheduled to be back on the Net by late summer. Why not all of the stations? "It's a pretty big undertaking just to get 250 stations in the top markets up and running," says Hiwire spokesman Wayne Hickey. Hiwire's service will ask would-be listeners for their age, gender and ZIP code so the Internet-only ads can be targeted to each customer.

Smaller radio-station companies are also getting back online. Jefferson Pilot Communications, which operates about 20 stations in seven U.S. cities, made an ad-insertion deal with RealNetworks last December and plans to have its stations back online by summer's end. Jefferson Pilot's stations will use RealNetworks technology to swap the ads local listeners hear with Internet-only ads.

Julene Snyder is a writer in San Diego.