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FIGURE 4-2 James Clark Maxwell RELIABILITY, SAFETY, AND COMPLIANCE 139

the robot can affect other electrons over a distance, the popular notion of interference.
Interference coming out of the robot can be measured with antennae outside the robot.
To illustrate this effect, take an AM radio and tune it between stations, where only
static is heard. Turn up the volume and put the radio down next to the computer. Execute
a few computer programs to exercise the computer. The inner workings of the computer
will be audible on the radio!
So how do we prevent the generation of interference inside the robot? First of all, we
cannot prevent it completely. All electrical systems generate interference. The trick is
to keep it well below the tolerable levels prescribed by the governmental groups that
regulate it. The Federal Communications Commission (FCC) does this, and many for-
eign governments enforce the CE mark overseas. Many techniques are available for lim-
iting the amount of electrical emissions generated within a robot.

Use Low Frequencies

All electrical signals emit interference, but lower-frequency signals tend to emit less.
Further, the FCC is more worried about higher frequencies than lower. As an example
of what can be done, some computers are optimized to run at clock frequencies of 32
kHz. This is a much slower clock than most computers have. As long as the computer
is fast enough to accomplish its work, such a clock speed will suffice. Don’t run the
computer in the robot at clock speeds that are greatly faster than needed.