electric current by means of the oscillograph. A photograph
made in this way of an alternating current--it is very much like
the curve shown in Fig. 15.
Fig. 16 shows an oscillograph picture of the current flowing
in the loud-speaker circuit. Note that the current is not
Fig. 15
uniform in this case--it is the electrical way of saying ''Hello"
and is of course an "audio" current.
Values are not given in these pictures, of course, and frequently
they are not needed--it is enough merely to get a picture
Fig. 15
of the current so that by comparing it with the pictures
stored up in our minds we can tell what sort of a current it is.
Radio-Tricians and Radio engineers use these curves so
much in their work that they often draw them free-hand just
as you would sketch a picture or a diagram--when it is not
necessary to show actual values of the variations in current flow.
