In the design of large and complex digital
systems, it is often necessary to have one device communicate digital
information to and from other devices. One advantage of digital information
is that it tends to be far more resistant to transmitted and interpreted
errors than information symbolized in an analog medium. This accounts for
the clarity of digitally-encoded telephone connections, compact audio disks,
and for much of the enthusiasm in the engineering community for digital
communications technology. However, digital communication has its own unique
pitfalls, and there are multitudes of different and incompatible ways in
which it can be sent. Hopefully, this chapter will enlighten you as to the
basics of digital communication, its advantages, disadvantages, and
practical considerations.
Suppose we are given the task of remotely monitoring the level of a water
storage tank. Our job is to design a system to measure the level of water in
the tank and send this information to a distant location so that other
people may monitor it. Measuring the tank's level is quite easy, and can be
accomplished with a number of different types of instruments, such as float
switches, pressure transmitters, ultrasonic level detectors, capacitance
probes, strain gauges, or radar level detectors.
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