Ghost calls have long been a staple of horror movies and urban legends involving frightened baby sitters. Ray Bradbury wrote a teleplay about a telephone switch that reached consciousness only to start stalking a person.

But the culprit behind what is becoming a common occurrence in some households may have a less than otherworldly explanation. More often than not, it is a telemarketer -- and one that complies with federal regulation. Indeed, following the rules may be one reason for the ghost calls.

Most fingers point at telemarketers who use a predictive dialer, a device that makes hundreds of calls a minute and uses artificial intelligence to detect when a person answers. These are then connected directly to a telemarketer waiting to talk about a low mortgage rate, political candidate or a once-in-a-lifetime opportunity. If no one in the cubicle farm is ready to start pitching, the predictive dialer just hangs up.

Rick Morris, the chief operating officer of the predictive dialer company TouchStar, said that regulations require dialers to hang up so abruptly. If no agent is available within two seconds, he said, the predictive dialer must hang up, because the Federal Communications Commission says the dialers cannot monopolize a line.

"We didn't want to tie up their line in case of an emergency," he said.

Some consumers are trying to find out what is behind ghost calls by collecting data. When Michael Hirsch, a Web master for a local-government Web site in Salisbury, Md., gets ghost calls, he logs his experiences on whocalled.us, one of a number of Web sites devoted to unraveling the mystery of the calls.

"I've had my phone number 20 years, and I'm very seriously thinking of changing it," he said with the frustration of a man who has been interrupted too often.

Whocalled, 800notes.com, numberzoom.com and similar sites collect notes from anyone who received a phone call and wants to know a bit more about the number on the caller ID screen. Whocalled has logged almost 400,000 calls and identified about 92,000 numbers. Hirsch said he is planning on hooking up the Web site to his computer to filter out the worst offenders.

Consumers take action

Julia Karelina and Mike Bravo started 800notes.com, which tracks ghost calls as well as known swindles and unsolicited faxes. Karelina said she is proud that the site recently persuaded a nonprofit group to fire a telemarketer after the organization noticed all the complaints on the site.

Because the predictive dialers try to identify answering machines by measuring the amount of time someone or something speaks, one way to defeat them is to give a long greeting, as an answering machine does, rather than a simple hello followed by a pause.

Hirsch follows up his posts to whocalled.us with complaints to the local Better Business Bureau and state regulators.

Hirsch includes the telephone numbers and addresses of these groups in his posts to the site so that others who visit can file their complaints with ease.

Hirsch said he remains optimistic about his chances, saying, "It's so new that people don't know that they can go there and put in their experiences and find out that others are having the same problems.

"If we don't nip it in the bud, it will escalate just like e-mail spam has."

No one knows how the battle between the humans and technology will play out.

In Bradbury's story, the man tracking the ghost calls traces them to a box on a telephone pole. Then it electrocutes him.

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