Broadcast fax is the ability to send a single fax to more than one person at the same time [source: Answers.com]. Some fax machines can scan a document once and broadcast it to multiple recipients. But, when most people talk about broadcast fax, they're referring to third-party services that use fax server technology to send a single fax to hundreds or thousands of recipients at once.

Photo courtesy Dreamstime Broadcast fax allows you to send more than once fax.

Broadcast fax is a powerful tool for public relations professionals, who routinely send time-sensitive story ideas to hundreds of targeted journalists and publications simultaneously. According to a report by Davidson Consulting, broadcast fax was a $200 million industry worldwide in 2006.

Unfortunately, broadcast fax is also a powerful tool for fax spammers who flood thousands of fax machines with unsolicited "junk fax" advertisements, despite strict, Federal anti-spamming laws.

In this HowStuffWorks article, we'll look at the technology behind broadcast fax, its real-world applications and the legal issues surrounding its use and misuse.

Let's start with a look at fax servers, the key technology behind broadcast fax.