91、If we consider binary transmission, the complete information about a particular message will always be obtained by simply detecting the presence or absence of the （pulse）.
92、The problem is easily overcome by specifying a frame （format）, where at the start of each frame a unique sequence of pulses called the frame code, or synchronization word, is placed so as to identify the start of the frame.
93、The fundamental problem encountered by all serial data（transmission）systems is how to split the incoming data stream into individual units (i.e., bits) and how to group these units into characters.
94、The most critical aspect of the system is the receiver timing. The falling edge of the start bit triggers the receiver's local （clock）, which samples each incoming bit at its nominal center.
95、A primary objective of the OSI reference （model） is to accelerate the development of future networking products.
96、In the OSI reference model, there are seven numbered layers. Each （layer）illustrates a particular network function.
97、The Internet is an international collection of computer（networks）that all understand a standard system of addresses and commands, connected together through backbone systems.
98、A voice channel occupy the （range）300 Hz to 3.4kHz.
99、There are many different （schemes） for performing these three functions.
100、Each value is coded as a（sequence） of 8 binary digits.
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