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BELLS, ALARMS, AND ANNUNCIATORS 149

The armature is made from a strip of sheet-iron. It is
pivoted on the frame at its upper end. The strip is bent
at right angles so as to fall in front of the magnet. The
lower part of the armature is bent into a hook. The hook
fits into a slot cut in the drop bar. A fine wire spring is
placed between the frame and the upper end of the arma-
ture so as to pull
the armature away / 1-.- / E._,,~__
from the core when I
the current is not i O

'1:

 

 

 

passing through the
magnet.

The electromag-
net should be wound
withNo.25B.&S.1 0 ,.
cotton-covered mag-
net wire. FIG :29. — Details of the Drop-Frame and

When a current is Amat‘m”
sent through the magnet, it will draw the armature in.
This action releases the hook from the edge' of the slot in
the drop bar and permits the bar to drop and bring the
number or letter down into view.

A number of “ drops ” may be arranged on a board and
placed in difierent circuits'so as to indicate which circuit is
closed at any time. It is a good plan to arrange a bar to
act as a stop, so that the numeral will not drop down too
far. Each time that any one of the drops falls, it must be
reset by pushing the bar back into position.

 

 

    

 

 

 

AR MA TURE

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