What really bothers Leslie L. Byrne is the silence: the pregnant pause that hangs in the air after she's picked up the ringing telephone.

Who's there?

Too often, no one. Like a scene from a horror movie, there's only dead air. Byrne, a Democratic state senator from Fairfax, would like to kill that phantom call, the result of modern technology that allows telemarketers to keep their sales agents as busy as possible.

For the fourth consecutive year, Byrne has introduced legislation that would allow Virginians annoyed by unwanted marketing calls to add their names to a statewide do-not-call registry. Another element of the bill: limits on what the industry calls "predictive dialers."

Byrne isn't alone in her antipathy toward predictive dialers, which many people find even worse than a salesperson interrupting the baby's bath with a pitch for telephone service or a cemetery plot.

"I hate when I pick up the phone and no one's there," said Karen Taylor, 33, of McLean. "Or they say, 'Please hold while we connect you to the next person.' "

Said Judith Vogel, 67, of Fairfax: "That would be great not to get those [phantom calls]. Sometimes I'll wait and eventually you get that recording: 'If you want to make a call, please hang up.' I want to say, somebody called me."

Well, not somebody. Something. Predictive dialing is a technological marvel that allows telemarketers to squeeze as much as they can out of the industry's most expensive element: people. Working from a list, a computer -- which can dial a telephone much faster than a jabbing human finger -- dials batches of phone numbers at a time, weeding out disconnected lines, answering machines and busy signals as it encounters them.

Also programmed into the computer are complex algorithms based on the length of a typical sales call. When the computer predicts that a human telemarketer will be free to make another pitch, it transfers a customer.

"But if you make the system too aggressive it could dial a number and there's not an agent available," said Dudley J. Larus of Amcat, an Oklahoma-based company that makes call center products. "Why? Because it's actually dialing the numbers before the agent is finished with the previous call. If it waits, then there would be times where [agents] were just sitting there waiting for the next call."

Sometimes the computer overestimates on its educated guess. And so, as with Lucy and Ethel at the candy factory, the calls keep pouring in. If no agent is available, the computer terminates the connection, usually before a consumer answers, but sometimes after.

The telemarketing industry calls the phantom rings "dropped calls." Think of them as the bonbons that tumble off the conveyer belt.

Byrne has had enough. "I've had constituents who thought they were being stalked because the phone kept ringing and they kept being hung up on," she said.

Then there's the pause, the brief gap between when you pick up the phone and a telemarketer starts talking. The pause is a result of the time it takes for the dialing system to transfer the call to the next available agent.

While the dropped call is an irritant, the pause is not without some utility, say those who find phone pitches an annoyance. "I usually use that opportunity to hang up," said Maryland state Sen. Brian E. Frosh (D-Montgomery), sponsor of a do-not-call bill.

Frosh's bill doesn't target predictive dialers. It requires Maryland's Public Service Commission to create a database of residential telephone subscribers who choose not to receive phone solicitations. Marylanders would be able to sign up for free. In Byrne's approach, Virginians would pay $10 to get on the list, with a $5 annual renewal, money used to administer the database. Companies that call a number on such lists can be fined -- $500 per call under Byrne's prescription.

Do-not-call bills have been introduced in Maryland and Virginia for several years but have died in committee, which proponents blame on lobbying by the telemarketing industry. A District bill proposed two years ago by D.C. Council Chairman Linda W. Cropp (D) also died.

Elsewhere, do-not-call lists operate in 28 states. Massachusetts started its registry Jan. 1. In the first week, 400,000 residents signed up for it via the Internet or by calling a toll-free number. California's list goes up April 1. And the Federal Trade Commission has proposed creating a national do-not-call registry, which would require congressional approval.

The FTC isn't waiting to regulate predictive dialing. The agency has prepared rules stipulating that no more than 3 percent of a telemarketer's calls per day can be dropped, and that a person or sales pitch-free recorded message must come on the line within two seconds. The rules go into effect 60 days after publication in the Federal Register, which is expected within weeks.

G.M. Matt Mattingley, director of government affairs for the American Teleservices Association, said the industry has been policing itself, hewing to an informal 5 percent dropped call rate.

"Our objection all along to these types of legislation is that there is a supposition that every time you pick up the call and there's nobody on the line, then it's a predictive dialer," said Mattingley. "It's as if the wrong number has disappeared from the American scene."

Others in the industry point out that predictive dialing can be a force for good, allowing schools to quickly notify parents of early dismissal, for example. Dropped calls and pauses can be eliminated, said Amcat's Larus, if the system is "properly tuned."

As for the do-not-call lists, the telemarketing industry says they put a crimp in consumers' choices. "Nobody who buys from a telemarketer wakes up thinking, 'I hope a telemarketer calls me today,' " Mattingley said. But, he said, when they hear details about a specific deal that interests them, they're glad they answered the phone.

The bills that are sweeping state legislatures and percolating on Capitol Hill are wrongheaded and anti-business, said Mattingley. "Politicians recognize that there's no risk in bashing a telemarketer because nobody's going to stick up for them."

Byrne is unmoved. "I'll keep pushing," she said. "I think most people feel the same as I do: You ought to have some control over the telephone you pay for."