Starting Sept. 1, many of the pre-recorded calls that seem to come in just as you're sitting down to dinner will become illegal.

Recent amendments to the Telemarketing Sales Rule (TSR), the main federal statute governing telemarketing practices, include prohibitions against a large number of so-called "robocalls." The changes, announced over a year ago, are set to go into effect at the beginning of next month.

There are a few catches, however. First, purely "informational" calls are exempt under the new rules. Thus, those calls from Orbitz announcing that your flight is departing two minutes later than expected will not be subject to a penalty.

Perhaps more annoyingly, public service announcements are exempt from the new rule, as are political calls. Political robocalls are especially common during election season, and aren't likely to stop anytime soon. Banks and telephone carriers are likewise exempt from the rule.

The TSR amendment, approved by the Federal Trade Commission (FTC) in August 2008, subjects violators of fines up to $16,000. The regulation doesn't apply to calls from a live telemarketer--"Robocall" refers pre-recorded message that is played back when you pick up the phone.

Consumers can waive the prohibition by giving companies written permission to contact them.

The FTC, which oversees and enforces the TSR, has already asked consumers to be on the lookout for calls that violate the new policy. Consumers can also report violations by calling 1-877-FTC-HELP.

As FTC Chairman Jon Leibowitz put it in a news release, "American consumers have made it crystal clear that few things annoy them more than the billions of commercial telemarketing robocalls they receive every year."

Leibowitz urged consumers being "harassed by robocallers" to "let us know, and we will go after them." Lois Greisman, associate director of marketing practices, echoed Leibowit'z sentiment, pledging that the FTC "will enforce them [the new rules] vigorously."

Consumers who want additional protection from telemarketers should add their name to the federal Do Not Call Registry.

How clear-cut the rules are remains to be seen. Telemarketing rules are notorious for inviting court challenges, given the extent to which certain industries rely on them. The Do Not Call Registry, originally scheduled to go into effect in 2003, was delayed by a series of court challenges challenging the law's constitutionality. An appeals court decision the following year allowed the law to take effect.