WASHINGTON  The Federal Communications Commission approved a proposal on Thursday that would open vast amounts of unused broadcast television airwaves for high-speed wireless broadband networks and other unlicensed applications.

The change in available airwaves, which were freed up by the conversion of television signals from analog to digital, constitutes the first significant block of spectrum made available for unlicensed use by the F.C.C. in 20 years.

It was a victory that did not come easily, or quickly, however. The F.C.C. first approved a similar measure in 2008, but the technical requirements for unlicensed devices drew objections from 17 companies or groups on both sides of the issue, forcing the commission to redraft its proposal.

While computer and Internet companies like Google, Microsoft and Dell favored the idea, television broadcasters worried about possible interference problems.