ENVS 1200 Lecture Notes - Lecture 19: Discrete-Time Signal, Video Card, Bit Rate
ENVS 1200 Tutorial 19 Notes – The fundamentals of signaling technology
Introduction
• Signals are the means used to communicate data.
• A signal is carried on a communication channel as an electrical voltage, an
electromagnetic radio wave, or a switched light.
• Data is represented by changes in the signal as a function of time.
• The signal may take on a continuous range of values, in which case it is known as an
analog signal
• It can take on only discrete values, in which case it is known as a discrete signal.
• A binary discrete signal is usually called a digital signal.
• A representation of a signal shown as a function of time is called a waveform.
• An analog signal and a digital signal
• We are primarily interested here in analog and digital signals
• Although e ote i passig that the aalog ideo sigals goig to a display fro a
computer video card takes on only specific values, 16 or 256
• Some different number of values depending on the video adapter used, and are
therefore more accurately considered to be discrete rather than analog or digital.
• We shall not consider discrete signals further here, although discrete signals are used in
certain cases to increase the bandwidth of a channel.
• For example, discrete signals are used to increase the speed of a modem beyond its
basic bit rate.
• Computer data is fundamentally digital in nature.
• A digital waveform on a channel might represent a sequence of bits of data representing
a text file, for example.
• Sound is analog.
• The loudness of sound coming from a stereo speaker would be represented by a
continuously changing waveform.
• Represented by changes in the signal as a function of time.
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