ENVS 1200 Chapter Notes - Chapter 11: Digital Data
13 May 2018
School
Department
Course
Professor
ENVS 1200 Chapter 11 Notes – Summary
Introduction
Digital Signaling
• Digital data being carried by a digital communication channel is already in correct
format, so theoretically no conversion is necessary.
• In practice, the situation is somewhat different.
• Since there is no carrier present on the channel, there may be no way to detect a string
of bits at the receiving end of the channel for some signals.
• The signal for example, consists of a string of twelve zeros, ut theres o a to tell.
• A 0 is represeted a alue of 0 olts, ad the state of the lie he o sigal is
present is also 0 volts.
• Obviously, there is no way to determine the presence of this signal.
• This example shows one difficulty in coordinating digital data that is transmitted from
one node to another.
• Oe oious a to sole this prole is to use a differet alue for the 0 it, sa, −5
volts.
• This solutio helps soehat, ut e still at tell oe it fro aother i the data
stream.
• As another example, consider a related problem, a steady stream of bits across a
communication channel from one computer to another.
• Suppose that each group of 8 bits forms a byte.
• If the stream is continuous, how does the receiving computer know how to group the
bits into bytes?
• Some method of synchronizing digital signals between the sending computer and the
receiving computer is always necessary, to be able to identify the position of each bit
successfully at the receiver.
• The basic problem is that the sending computer may opt to transmit data at any time,
and the receiving computer has no way of knowing when data will actually be sent.
find more resources at oneclass.com
find more resources at oneclass.com
