PSSA Passage by keralaguest


									PSSA Passage & Questions: Read the following passage and then answer the questions that follow.

                                               Signals and Communications
        Microwave transmission allows you to make telephone calls across deserts or other areas without wires or fiber-
optic networks. But how could you call a friend who lives across the ocean in Australia?
        In the past, your call would have been carried by one of the cables that run across the ocean floor between
continents. Because there are so many telephones, online computers, and fax machines today, the demand is too much
for these cables. Communication satellites that orbit the Earth help send these messages.
        These satellites use solar power to generate electricity. This allows them to operate receivers, transmitters, and
antennas. These satellites receive and send microwaves just like telephone towers. Because they are so high above the
ground, these satellites can relay signals between telephone exchanges thousands of kilometers apart.
        A satellite receives a microwave signal, called an uplink, from a ground station on Earth. The satellite then
processes and transmits a downlink signal to another ground station. To keep the signals separate, the uplink signal
consists of electromagnetic waves with a frequency of around 6 GHz (gigahertz, or 10*9 Hz), while the downlink signal
typically has a lower frequency of about 4 GHz.
        For maximum efficiency, the transmitting antenna of a communications satellite must be aimed so that covers the
largest area of land without the signal becoming too weak. This area is called a satellite footprint. The satellite footprint
increases as the distance between the satellite and Earth’s surface increases. With several satellites with large footprints,
a signal from one location can be transmitted and received anywhere in the world.

According to the passage, which of the following statements is correct?
   a. communications satellites are most useful when they orbit close to Earth.
   b. Transatlantic cables are capable of handling all telecommunications between Europe and the Americas.
   c. Twenty years ago, it would have been impossible to telephone someone who lived in Australia.
   d. Today, people use more communications technology than they have in the past.

What energy source do communication satellites use to generate electricity?
   a. solar
   b. atomic
   c. hydroelectric
   d. interal combustion

According to the selectrion, what is the Earth-to-communications satellite signal called?
   a. cable network
   b. uplink
   c. downlink
   d. footprint

What is the style and intended audience of this selection?
   a. simplified explanation of a technical subject for the general public
   b. technical explanation for electrical engineers
   c. non-technical explanation of a fictional subject for the general public
   d. highly technical explanation for electrical engineers

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