Oak
or walnut are the best woods to use for the lever, being more resonant than
the softer woods, and for the standard B and stop V. Any common wood is
good enough for the base A.
The lever L is 6 inches long, 1/2 inch deep, and 3/8-inch wide, and is
pivoted at a point 4-1/4 inches from the stop end. The hole should be bored
through it as squarely as possible, so that it may lie centrally without B
being out of the square. A piece of metal is screwed to its top face under
the adjusting screw S1.
The spring is attached to L and A in the manner already described on p. 89
in connection with the "buzzer."
The plate P2 should be stout enough not to spring under the impact of the
lever. Fig. 36 is an end view of the standard B. The drilling of the pivot
hole through this requires care. The screw S2 should be so adjusted as to
prevent the armature actually touching the cores of the magnets when
attracted. The ends of the magnet winding wire, after being scraped, are
clipped tightly against the base by the binding posts T1 T2.
If sounders are used in place of buzzers they are connected up with the
keys, batteries, and line wires in the manner shown in Fig.
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