Microwave communication uses （） -frequency radio waves that travel in straightline sthrough the air. Because the waves cannot （） with the curvature of the earth, they can be （） only over short distance. Thus, microwave is a good （） for sending data between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of "dishes" or （） . These can be installed on towers, highbuildings, and mountain tops.
Because the waves cannot （） with the curvature of the earth.Microwave communication uses （） -frequency radio waves that travel in straightline sthrough the air. Because the waves cannot （） with the curvature of the earth, they can be （） only over short distance. Thus, microwave is a good （） for sending data between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of "dishes" or （） . These can be installed on towers, highbuildings, and mountain tops.
Microwave communication uses （） -frequency radio waves that travel in straightline sthrough the air.
Under normal conditions the act of communication requires the presence of at least two persons: one who sends and the other who receives the communication. In order to communicate thoughts and feelings, there must be a conventional system of signs and symbols which means the same to the sender and the receiver.
The means of sending communications are too numerous and varied for systematic classification; therefore, the analysis must begin with the means of receiving communication. Reception of communication is achieved by our senses, of which sight, heating and touch play the most important roles.
Examples of visual communication are gesture and mimicry. Although both frequently accompany speech, there are systems that rely solely on sight, such as those used by deaf and dumb persons. Another means of communicating visually is by signals of fire, smoke, flags, or flashing lights. Feelings may be simply communicated by touch, such as by hand-stroking. Although a hi
A. communication depends on a conventional system of signs and symbols
B. only through our senses, can we communicate
C. to classify the means of sending communications is a very difficult task
D. there are more means of receiving than of sending communications
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