9 February 2005—Firefighters know what to look for inside a burning building. But until very recently, firefighters in New York City's tall buildings had too little assurance that they'd be able to tell each other what they were seeing. The New York City Fire Department's radio system often failed to get messages through collapsed walls or exposed steel. With two innovations, the department is working to change that.

One development is the brainchild of a retired department captain, who designed portable repeaters, high-powered radios that a fire chief can carry to a burning high-rise. A repeater works basically like an amplifier, picking up short-range radio traffic and carrying it over greater distances. A chief can carry the 9-kilogram repeater, called the Command Post Radio, to a burning high-rise and install it in the lobby or on the floor below a blaze. A separate effort involves putting new wiring inside tall buildings and subway tunnels to carry these conversations along so-called leaky cables when concrete and steel block the airwaves. Such a cable, 300 meters long, was installed last summer in the landmark Chrysler Building's elevator shaft.

The innovators care less about a radio signal's fidelity than about its ability to get through rubble and confusion. The department tried to improve the sound quality of all its radio communications in 2001 with a digital network from Motorola Inc., Schaumburg, Ill. But firefighters found the new network counterintuitive, in part because it eliminated hints about changing conditions. An analog radio would produce static if, say, a large steel beam suddenly blocked a firefighter's path. A digital signal, in contrast, would just cut off, leaving other firefighters to guess whether a colleague was in trouble. Today's simpler innovations aim to eliminate confusion during a crisis. That lesson sank in amid the agonies of the World Trade Center attacks.

Radio spectrum is as precious as oxygen to firefighters managing a crisis. Fire chiefs traditionally have used one dedicated channel, firefighters with handheld radios another. Some large buildings have their own channels, which provide wireless spectrum when disaster strikes. Repeaters in these buildings pick up signals from far-flung floors, to keep personnel in contact during an emergency. But they're useless if firefighters are talking into the wrong channels, and a system that relies on installed repeaters can leave firefighters stranded if those repeaters stop working. The new portable repeaters and the leaky-cable innovation both try to minimize the risk of confusion or repeater failure.

The crowding of firefighters and chiefs at the World Trade Center right after the September 11 attacks "was unheard of," former fire commissioner Thomas Von Essen told the 9/11 Commission. In the tumult, some evacuation orders from chiefs in the lobby seem never to have reached personnel on upper floors. For some chiefs, Von Essen testified, the repeater already in the building "didn't appear to be working properly." But both the National Institute of Standards and Technology and the 9/11 Commission concluded that the problem may have come from operator error. The 9/11 commission reports that chiefs pushed a button to listen on the repeater channel—but not a button to transmit. "It is unknown whether the lobby chief ceased to communicate on the repeater channel because of technical problems or because he…switched channels in order to…communicate with chiefs outside the South Tower," a footnote in the commission's report reads.

Unlike the World Trade Center, most tall buildings don't have repeaters installed. Mike Stein, a retired captain, invented the Post Radio in 2002 to give chiefs every chance to be heard. The radio's virtue is its portability. A chief carries it to a floor below a fire, Stein explains, to manage communication between firefighters on high floors and chiefs in a lobby. Stein programmed the 45-watt unit to work at the emergency broadcast network's highest zone of radio spectrum, which can accommodate more traffic than lower frequencies can. Each Post Radio costs around US $3500, says Stein, drastically less than buildings would have to pay to install repeaters.

Even so, the 75 Post Radios already deployed don't cover all potential disasters. "We're able to [use them to] communicate throughout the building 90 percent of the time," says Stein. For the other 10 percent—buildings with very thick floor plates or lots of structural steel, among other complicating factors—leaky cable could be installed to supplement. "The more metal and concrete you have, the greater the [signal] attenuation is," says Ron Haraseth, who directs automatic frequency coordination for the Association of Public-Safety Communications Officials International, in Daytona Beach, Fla. Leaky cable can carry signals all the way up a building—or through an underground tunnel.

The technology, used for years in mines, carries radio waves up a cable with slits cut into it. The cable receives signals from nearby handheld radios through the slits and carries them along its length. "The antenna is run through a shaft and signal leaks out," says Keith Brooks of Altech Electronics Corp., a specialty manufacturer in Brooklyn, New York, that builds the Post Radios. "You're taking the signal up the cable rather than over the air, so you don't have to pierce steel and concrete." Altech proposed installing leaky cables in the New York City subway system and in one office tower as a demonstration. The Chrysler Building's owners volunteered to house the demonstration in the art deco landmark's elevator shaft; Brooks supervised the installation last summer.

The leaky cable can come through when a repeater fails for any two firefighters trying to talk to each other amid wreckage and smoke. Because Brooks wants leaky cables to serve firefighters in chaotic situations he and Stein programmed the Chrysler Building installation to run on only one set of frequencies. No firefighter in a devastated skyscraper would have to worry about changing channels to reach colleagues elsewhere in the building. As long as a firefighter is inside the building, slits in the cable should pick up signals from his or her radio and pass them along to colleagues.

This isn't the first leaky cable to be used in a building—indeed, there was one in the basement of the World Trade Center. But it may be the biggest. Brooks installed a more pliable cable than what was found in the World Trade Center's basement from Victor Products USA Inc., a unit of Federal Signal Corp., in Oak Brook, Ill. The system was designed to run through underground mines up to 25 kilometers long. Vinyl-coated steel clamps hold the cable in place next to an elevator shaft. Stein guesses the installation cost roughly $10 000.

Repeaters and leaky cables will probably form much of the fire department's communication arsenal for the next few years. In late August, Stein and Altech oversaw a leaky-cable installation in subway tunnels south of 59th Street; Consolidated Edison Co. of New York, the electric utility, has connected repeaters to a leaky cable in a tunnel under the East River. If the cable breaks, Stein says, a repeater in Manhattan can broadcast radio signals across the river to Queens and vice versa.

These thrifty innovations make radios more reliable without retooling the network or forcing firefighters to learn counterintuitive new procedures. But the hardest part is anticipating how firefighters will use the equipment.

Alan Reiss, director of the World Trade Center for the Port Authority of New York and New Jersey when it collapsed, notes that agencies can communicate unclearly in a crisis for reasons having nothing to do with radio frequency. He says technology needs to fit into a robust "incident command system," or set of procedural rules, through which "all agencies are represented, and then the information is disseminated by each agency back over their own radio networks." Even then, what firefighters hear may not govern what they do. In the World Trade Center, the 9/11 Commission reported, "some firefighters were determined not to leave the building while other FDNY personnel remained inside and, in one case, persuaded others to remain."