ENVS 1200 Lecture Notes - Lecture 18: Analog Transmission
13 May 2018
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ENVS 1200 Tutorial 18 Notes – Electrical Voltage
Introduction
• Analog transmission uses a continuously varying waveform to carry data.
• Digital transmission carries data in digital form, using two different values of electrical
voltage or current or an on/off light source.
• The choice of digital or analog transmission signaling depends upon a number of factors.
• Some media are only suitable for one or the other.
• Where either is suitable, the choice is made on the basis of other factors such as noise
characteristics, the application, the bandwidth requirements, and other uses for which
the channel is to be shared.
• Except where analog transmission is required by the medium, there is a strong tendency
toward digital transmission in most circumstances.
• Digital transmission has the advantage that it is less susceptible to noise and
interference, which means a higher likelihood that the original data can be reproduced
exactly, error-free, at the receiving end of the channel.
• Digital transmission is also simpler, more efficient and more economical.
• When a digital signal is to be transmitted on an analog channel, it is necessary to
convert the digital signal into a form suitable for analog transmission.
• The converse is also true.
• The methods of conversion, and resulting limitations, are discussed
• It is also possible to share a channel among multiple sender-receiver pairs, using one of
several multiplexing techniques.
• Digital channels use time division multiplexing (TDM).
• Analog channels can also use time division multiplexing, but most use frequency division
multiplexing (FDM) instead.
• There are several important variations on these two primary methods, as well.
• Again, digital technology has an advantage
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