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How do you turn on the shower? (Example 2)
This
picture shows a shower head with an on/off
control. This is convenient, but together
with the shower control below presents a potential
problem. The problem is that both controls have
to be turned on or the shower won't work. If
either one or the other or both are turned off,
the shower won't work. There really isn't
any good way to tell which one needs to
be turned on. Thus, there are three ways
for the shower to fail to work and only
one way for it to succeed!
Design suggestion
When you design a set of controls, try to minimize the number of ways for them to fail to work and maximize the number of ways for them to succeed.
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Copyright © Michael J. Darnell 1996-2010. All rights reserved.
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