Previous Index Next
Page 305
(previous) (Page 000305) (next)
 
276 THE BOY ELECTRICIAN

inch between them, the filings will about half fill the
space.

The filings must be very carefully prepared, and in order
to make them, first use a. coarse-grained file on the edge
of a five-cent piece. Do not use the fine dust and powder,
but only the fairly coarse filings. Mix a few silver filings
from a ten-cent piece with the nickel in such proportion
that the mixture is 90% nickel and 10% silver.

You will have to experiment - considerably to find out
just the right
a m o u n t o f
filings to place
in the tube,
and how far
apart to place
the brass rods

«all! [Ill-[1‘]!

 

 

 

 

 

 

 

FIG. 234. —Details of the Coherer. or plugs°
Remove the

gong from an old electric bell and mount the bell on the
base as shown in Figure 2 3 3. It should be in such a posi-
tion that the bell hammer will touch the coherer very
lightly when the bell is ringing.

The two binding-posts, tube, rods, and filings constitute
the coherer. The bell is the decoherer. '

The next thing required in order to complete the appara-
tus is a relay. You may use the relay described in Chapter
X or build one according to the plan shown in Figure 235.
This relay consists of a single electro-magnet mounted

I

Previous Index Next