Public safety officials have wanted such a seamless communications system ever since the 9/11 terrorist attacks. The sweeping changes are even more remarkable because they resulted not from an effort to address communications policy, but from a hard-fought bipartisan compromise to extend a payroll tax holiday and jobless benefits. Republicans insisted that the extension of the unemployment insurance — a cost of roughly $30 billion — be paid for in full, and one area that both sides could agree on was spectrum sales.

The spectrum auctions are at least one to two years away, but most of the programs they pay for would be covered immediately. Consumers are unlikely to see additional charges since the auction would add new spectrum rather than adding to the costs of existing spectrum.

The payroll tax exemption would be extended through the end of this year, providing a worker earning $50,000 annually with $1,000 more in take-home pay over that time. The bill would also prevent a reimbursement cut for doctors who accept Medicare.

The legislation is the result of an unusual degree of cooperation between two parties that have fought bitterly over recent issues, and members of the conference committee that negotiated the deal played to the cameras on Thursday. One by one, members filed into the office of the committee’s chairman, Representative Dave Camp, Republican from Michigan, to sign the papers splayed out neatly on a large table that rested under an ornate chandelier.

Mr. Camp and his chief negotiating partner, Senator Max Baucus, Democrat of Montana, linked hands for the cameras, as Mr. Baucus said helpfully for anyone who did not get the visual cue: “Working together!”