Whenever a cellular phone broadcasts its signal, there really are two transmissions being emitted. There is the one you hear-the voice-and there is the carrier signal, which broadcasts at 4.5 MHz above the primary signal. The carrier signal gives a listening receiver the phone’s identification number, the frequency it is transmitting on, and the “cell,” or area, in which the caller is located.
All the technician had to do now was to wait for Jared to call again. Once the call came in, he would monitor the signal 4.5 MHz above the frequency of the call, thereby zeroing in on the cellular identification number.
That number would next be programmed into the linked computer, which was equipped with special law-enforcement software and had been preprogrammed with all existing cellular frequencies, provided by the FCC.
Cellular telephone calls constantly jump frequencies as the caller moves between cells, so the cellular phone tells the receiving cell-by means of the carrier frequency signal-when to do the “hand-off,” when to switch frequencies, and to which one, depending on which cell is strongest.
Knowing which cellular identification number to look for, the computer can tune the receiver, ever scanning, ever running its search program. That way it can quickly identify which cell the call is being made from.
With Jared inside a building-i.e., stationary-the task would probably be easier. That meant he was located within one “cell,” presumably somewhere in Manhattan.
If, that is, he called again.
Seven minutes after the technician arrived at Operation MINOTAUR’s headquarters, he did.
Sarah picked up the phone and heard Jared whisper: “Mom-”
“Jared, oh, thank God. You’re all right?”
“Yeah.” He said it with a trace of his usual petulance, which made Sarah smile with relief.
“Now, Jared, listen carefully. Don’t hang up, whatever you do. What does the building look like?”
“It’s-it’s a building, Mom, a modern building, I don’t know!”
“What’s the name of the bank?”
“It’s only on the first floor-”
“Which bank?”
“I think it’s Greenwich something-”
“Greenwich Trust! Jared, can you get out of there?”
“The room’s locked. It’s like totally dark in here.”
“Where is he? Jared, what’s he doing right now?”
“He’s-” Jared lowered his voice to a whisper that was almost inaudible. “He’s coming toward me. I can hear him right outside the door.”
Sarah’s heart drummed in her chest like a hummingbird’s. “Oh, God, Jared. Be careful.”
The technician, hunched at the receiver next to Sarah, said, “Getting there. Keep him on longer.”
She heard a voice in the background, a man’s voice, shouting something, and then she heard the phone clatter to the ground, and then there was Jared’s voice, a faint cry. “Help me!”
“Five more seconds!” the technician shouted.
But the phone was dead.
Panicked, Sarah turned around, saw Pappas watching wide-eyed, saw the technician hunched over the receiver.
“You didn’t-” she said, afraid to ask whether he had traced the call.
“Not yet,” he admitted.
“Oh, Jesus!”
“No, wait,” the technician said.
“But the line’s disconnected!”
“That’s all right,” he said. “The phone’s still on.”
“What do you mean?”
“Whether the phone’s in use or not,” the tech said, his eyes not leaving the computer screen, “still transmits… eight seven two point oh six megahertz…”
“What?” Sarah said.
“Long as the phone’s turned on-whether it’s in use or not-as long as the phone is powered on, it keeps transmitting back and forth to the closest cell. That’s how you can tell the strength of the signal before you use the phone. It’s-Yes! I got it!”
The open door to the supply closet cast a bright light on Jared, who, Baumann now saw, was speaking on a cellular phone. Who would have thought it? Baumann grabbed the child and placed a gag in his mouth. Over it he pressed a short piece of duct tape.
“Let’s go, little one,” he said, more to himself than to the boy. “Time to get going.”
CHAPTER NINETY
The cellular telephone company that served Sarah’s Motorola was NYNEX Mobile, which has 560 cell sites in the northeastern United States. In Manhattan, NYNEX has between thirty and forty cell sites; it prefers not to make public the precise figure.
When a call is placed from a cellular phone, whether mounted in a car or hand-held, the signal is relayed to the closest cellular site, which is little more than an antenna connected to sensitive radio-frame equipment. There are two types of antennas: directional, which is a rectangular box measuring three feet by one foot; and omnidirectional, which is straight and cylindrical, about an inch thick.
In cities like New York, these antennas are usually mounted on the roofs of buildings, except where a building is particularly tall, in which case they are mounted on the side of a building. The brains and guts of the cellular site, however, occupy an area approximately the size of a twelve-by-six-foot room, usually in leased space within the building itself. There, large radio-frame equipment receives and processes the signals, then sends them via telephone lines to regular telephone-company switching centers.
A cell may be as large as several square miles or as small as one building. This is because of the peculiarities of how Manhattan is built. The problem is not population density but topography: the profusion of extremely tall buildings with relatively narrow streets below. This makes it difficult for radio waves to travel to street level-where most cellular phones are used.
Because of the topography, for instance, there is a cell site in Rockefeller Center that serves an area of no more than two square blocks. There is even a cell site in a large Wall Street-area building that covers only that building.
The Wall Street region presents a number of problems for NYNEX Mobile, for several reasons. There is a large density of people in the area who use cellular phones. Also, many of those people use their cellular phones inside buildings, most of which are old, solidly constructed, thick-walled-and therefore difficult for radio waves to permeate. And the area has the same topographical challenges as Midtown-very tall buildings built on very narrow streets.
NYNEX Mobile compensates for those difficulties in two ways: by mounting some of their directional antennas on the sides of buildings, pointed down at the street, to maximize reception; and by placing more antennas per square mile in the region-four in the New York stock market area alone.
There are more cellular sites in the Wall Street area than anywhere else in the city, which means that each cellular site is relatively small-an area of a few blocks, instead of a few miles. This simple fact of telecommunications life in Manhattan turned out to be the very break Sarah needed.
NYNEX Cellular Site Number 269 was an area of approximately three irregularly shaped city blocks almost at the southernmost tip of Manhattan Island, near the South Street Seaport. The omnidirectional antenna received and transmitted signals to and from all NYNEX-serviced car phones and cellular phones situated within a chunk of real estate bordered by Water Street, Broad Street, Whitehall Street, and the one-block-long Stone Street. Running parallel to Stone, and dividing the almost-but-not-quite-rectangle into three wedges, were two short streets, Bridge and Pearl. Jutting into the rectangle from the Water Street side, and ending at Pearl, was Moore Street, one block long and paved in cobblestone.