Every Fourth of July, the streets of Rehoboth are blocked with traffic during the fireworks show, keeping fire trucks and ambulances from moving. The city calls in reinforcements from throughout the state and stations a crew on every other downtown street.

Before the 800-megahertz system, firefighters communicated by setting their low-band radios to the same frequency. But by July 4, the visiting crews had replaced their old radios with the new 800-megahertz models, ones that would allow far more users to be a part of the communications.

This year, more than 100 men and women from eight agencies expected to stay in contact with one another using the new Motorola portables hanging on their hips. With the visiting agencies all using the new 800-megahertz radios, Rehoboth officials decided to use the new system despite earlier tests showing it had problems.

That night, all of the high-tech equipment failed - again.

Rehoboth firefighters had to use their old 400-megahertz radios. They loaned a few spares to the outside crews, but there were too few old radios to go around.

At the resort's command post, Snyder, the assistant fire chief, couldn't reach everyone he needed. At one point, he used a hand-written note to send a paramedic crew out on a 911 call about someone who had been cut on the boardwalk.

About six square miles of the town is dead to Motorola's radio system, the victim of geography, said Ron Marvel, chairman of the Sussex County 800-Megahertz Committee.

Rehoboth's firefighters discovered this late last year, just before the new system was switched on in Sussex County. As they did July 4, the fire company occasionally experiments with the new radios, trying to make them work, Snyder said. But when they leave the station to answer a call, they use the old system.

The area has always had radio transmission problems because the town slopes toward the ocean and signals bounce out over the water. Because there is nothing at sea to reflect radio waves back into town, the signal is easy to lose.

Rehoboth fire officials solved that problem more than 10 years ago by building a 150-foot radio tower in town behind Fire Station No. 1. The new 800-megahertz tower is about 15 miles away, just west of Milton.

Earlier this month, a convoy of volunteer firefighters led state and Motorola officials around town demonstrating the system's outdoor flaws.

At one point, Marvel, the chairman of the Sussex County 800 Megahertz Committee, raised one of the new radios to his mouth to test the signal strength in Henlopen Acres.

'Testing one, two, three, four, five,' he said, speaking to a dispatch center 12 miles away in Georgetown. The dispatcher there responded, saying the signal was loud and clear.

But 3 feet away, the radio held by another volunteer firefighter remained silent, unable to pick up the transmission.

State and Motorola officials are confident they can erase Rehoboth Beach's dead zone and a similar problem in Kent County around Hartly.

The problem could be more complex in New Castle County. Despite having five of the 10 towers erected statewide, emergency crews in the county have had chronic problems.

New Castle County police officer Gus Zeissig was in Claymont June 26 when his radio failed.

Zeissig knew he was going to need help as he drove up to a fight outside the Stoneybrook Apartments that evening.

The area is on the edge of Claymont, where a 1993 Motorola computer model had predicted good radio coverage. At 5:10 p.m., as the temperature approached 90, the model turned out to be wrong.

Zeissig watched a crowd of 20 to 30 people gather around as a man and a woman argued heatedly in a car in front of him. He felt nervous about being surrounded, so he called for backup. But all the dispatchers a few miles away on U.S. 13 heard was an electronic gurgle.

Zeissig could hear them asking him what was happening at the scene, but it was obvious they could not understand his calls for help.

The incident ended harmlessly, with the man arrested on an outstanding warrant. But for several minutes, Zeissig said, he worried that the crowd might turn against him, or that the pair he needed to separate would attack him. Because of the radio failure, he said, he believed he was on his own.

'The calls don't stop because the system doesn't work, Snyder said. 'We just want them to fix it and we don't care who fixes it.

Richard R. Reynolds, a 55-year-old former Air Force radio technician, had been with the Office of Information Services for three years when he got the job of building a statewide radio system in 1989.

Until 1995, he was the only person assigned full time to oversee the project, one of the most expensive, most complicated contracts Information Services has ever handled.

'I was a one-man office,' he said.

That worried Bob Pedersen, manager of the Communications Division of the Department of Public Safety. Soon after he joined the division in 1994, he recommended that Information Systems add people to the project, he said.

'This is a pretty complex, large project,' Pedersen said.

Eventually another person was hired to work with Reynolds.

Information Systems director Jack Nold said his agency, which had sole responsibility for monitoring work with Motorola, did everything it could to make the project succeed.

'I don't think that there's anything that we would have done differently,' he said.

Nold's division never hired anyone to study what type of system the state needed, an unusual decision for such an ambitious project. Normally a public agency hires a consultant to decide what kind of network it needs, Motorola spokeswoman Pat Sturmon said.

Information Services also didn't hire a consultant to write the documents companies needed to submit bids for building the system. Instead, a committee of public communications experts wrote the requirements in 1991.

Those technical specifications were so flawed, state officials withdrew the documents and started over, Reynolds said. In the second round, officials were so confused by the different responses they abandoned that effort as well, he said.

For the third try, the state hired a California company to review the committee's work.

Motorola was the only company to respond. By the time Motorola got the contract, state legislators were no longer involved in the project, said Rep. Roger Roy, R-Limestone Hills. They had approved a general outline for a system they thought would work indoors, Roy said. Minner, who was in the Senate at the time, and Rep. Bruce Ennis, D-Smyrna, agreed. The three were on a state committee that decided what kind of system Delaware would buy. The committee then broke up and left the details to Information Systems.

Not hiring consultants early in the process put state officials at the mercy of Motorola, Warner said.

'That was a gross error,' he said.

State officials initially expected the system to cost $160 million, said John DiSalvo, head of wireless communications for Florida. But after the network was turned on in different parts of the state, and complaints about dead spots surfaced, the cost went up.

Florida taxpayers will have spent $350 million on the system by the time it is completed in 2003, DiSalvo said.

State legislators expected Delaware's project to cost up to $18 million, Minner said.

So far, the system has cost $51.7 million. Most of that increase came as legislators agreed to buy the new radios required for the system along with the towers and other equipment, Reynolds said. Police or fire agencies initially were expected to buy the radios themselves, but state officials later decided that would be too big a burden for them.

Earlier this year, Information Systems asked Carper and the General Assembly for $8 million more to fix and expand the system. The request was cut from the budget by the administration.

Although Motorola and state officials say the system is not as bad as firefighters and police officers say it is, they disagree on why there are problems.

Motorola says it fulfilled its 1993 contract and points to a test that the company says it passed.

State officials say the test was flawed.

The test set up grids in every county made up of quarter-mile squares. A square passed if a special radio picked up a signal on any 40-foot section of street in the grid and if a voice could be heard.

Under the contract, if 95 percent of the grids passed, Motorola fulfilled its obligations.

'Testing showed 97 [percent] to 98 percent coverage, said Steve Eckels, sales team manager for Motorola's mid-Atlantic division.

Information Services chief Nold said the testing probably does show a 98 percent success rate, but that doesn't mean the system works the way it should.

A single, short measurement is not enough to determine whether an entire grid can receive the signal, Reynolds said.

Last year, Baltimore put in the same Motorola system, but hired an outside consultant to help officials design a thorough test, said Assistant Chief Raymond Lehr, who oversaw the installation of that city's network.

The city required more grids per square mile to be tested. The city also decided where in each grid the test would be conducted, Lehr said.

'The testing was key to making it work,' he said.

State officials and Motorola executives say Baltimore's system was designed with high-rise buildings in mind, so the testing requirements were different.

Critics say state officials didn't buy enough towers for the new system. That's why there are problems on routine calls every day for officers, firefighters and paramedics, Warner said.

Motorola and state officials say Baltimore ordered a system that had to reach deep inside high-rise office buildings, so naturally, they needed more towers per square mile.

Public safety officials worry that someday a failed transmission could have disastrous consequences. A radio-caused delay could easily turn fatal, veteran New Castle County paramedic Lou Rombach said.

Paramedics use their radios to call emergency-room doctors for advice and to warn hospital staff that a patient is on the way and will need special treatment. Advance warning or quick advice from a doctor could mean the difference between life and death for a heart-attack victim, Rombach said.

'This is a safety issue for the union, said Ken Dunn, president of the county union that represents the paramedics. 'When I need help, I need it right away. If I need to talk to a doctor, I need to talk to them immediately.'

State and Motorola officials finished a detailed round of new tests earlier this month looking for solutions to the outdoor dead zones. Motorola, after months of prodding by Carper, last week agreed to install new equipment the company says will fill the reception holes.