of various receivers, and photographs of the different parts used
in them, you would get a very accurate mental picture. Therefore,
we use the photographs as "tools."
Now photographs are all right if we have them on hand or
if they are easy to get. But suppose we want to describe a new
kind of set, one of a kind that has never been built. No photographs
are available, of course, and yet we must have a picture,
to show you the picture that is in our minds. So we draw a
sketch, or several sketches, which will illustrate a word description.
Together they will give you the picture which we have
in mind.
Photograph
Sketch
Fig. 1
Sketches are often used instead of photographs, even when
these are available, because certain details can be brought out
and emphasized--while the camera makes no distinctions. The
camera often gets the high-spots only--it is very sensitive to
shadows--it doesn't see around corners. Often important details
are completely hidden--but in a sketch we can bring out these
important details and show everything clearly. See Fig. 1.
Now let us go a step beyond the sketch. Suppose a Radio
cabinet designer has a very original idea, he has in his mind a
picture of a cabinet different from any that has ever been built.
He draws a sketch of it, it looks good and he wants the cabinet
maker to translate the idea into wood. Does the designer merely
hand over the sketch to the cabinet maker and tell him to go
ahead and make it? No--the cabinet maker wouldn't know
from a sketch what size it should be, of what kind of wood it
should be made, he wouldn't know any of the dimensions.
