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Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice.
The first innovation in the design of combat binoculars(双筒望远镜)in over 200 years is on the horizon. The device, called "talking binoculars", is derived from the strategic satellite-to-satellite communications program. The idea is to use one pair of binoculars to project a laser beam to carry a scout's' observations to a second pair as the receiver.
Military scouts today cannot use radios during radio silent scouting missions inside enemy territory because the enemy can detect and locate their transmissions. With the new "talking" binoculars, when a forward military scout sees the enemy through transmitting laser binoculars and depresses the target locate and store button, global positioning system technology will measure the enemy's target position. Then, the binoculars store the information and use its invisible laser beam to transmit the enemy's position to a receiving set of binoculars. The receiving scout can then immediately transmit target data back to the lines. The military scout will no longer need maps, have to depend on written notes, or leave a position to report back to the commander.
The innovative binoculars also solve the aged-data problem by relaying the military scout's observations in near-real time to the commander in the tactical(战术的) operations center. The scout does not need to personally return to lines to make a report which is aged by the time the commander receives it.
"Enemy detection of the binoculars is near impossible because the weak laser beam is projected from point to point," Strickland said. "An enemy searching for a weak' laser source requires sensitive optical detectors and must be near the receiver to detect the weak laser. It will be much easier for the scout to see the enemy than for the enemy to detect the laser beam. By comparison, radio broadcast is transmitted in all directions, allowing easy detection by a prepared enemy from all angles." he said.
Digital laser communications is a valuable technology. Its advantage stems from providing high data rate communications capability when the mission prevents scouts from using their radios. A weak laser beam can carry digitized voice messages, targeting data and high-quality video images at extremely high data rates.
Military planners are already envisioning a day when all communications on a battlefield, between tanks or between tanks and helicopters, to name only two examples, are transmitted by laser. Theoretically, a laser-based communications system could handle 200,000 voice channels. Currently, even the most powerful high-capacity lasers, capable of transmitting 100 TV channels, weigh only 29 pounds, so they are easily deployed on vehicles or aircraft. In the future, lasers may also transmit information directly from orbiting satellites.
Without the talking binoculars, a scout during radio silent scouting missions ______.
A．can be easily detected and located by the enemy
B．is not able to determine the enemy's target position
C．has to make a record of what he has observed
D．risks getting caught when returning to report back
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