the gongs. The rebound of the gong is then taken up by
the elasticity of the tapper rod, which returns to an unflexed
position, and at about this time the pole piece releases the armature
so that it may swing over in the other direction to cause the tapper
to strike the other gong.

[Illustration: Fig. 181. Tappers for Dean Ringers]

The construction of the "in-tune" harmonic ringer employed by the Dean
Electric Company, of Elyria, Ohio, is illustrated in Figs. 180, 181,
and 182. It will be seen from Fig. 180 that the general arrangement of
the magnet and armature is the same as that of the ordinary polarized
ringer; the essential difference is that the armature is
spring-mounted instead of pivoted. The armature and the tapper rod
normally stand in the normal central position with reference to the
pole pieces of the magnet and the gongs. Fig. 181 shows the complete
vibrating parts of four ringers, adapted, respectively, to the four
different frequencies of the system. The assembled armature, tapper
rod, and tapper are all riveted together and are non-adjustable. All
of the adjustment that is done upon them is done in the factory and
is accomplished, first, by choosing the proper size of weight, and
second, by forcing this weight into the proper position on the tapper
rod to give exactly the rate of vibration that is desired.

[Illustration: Fig. 182. Dean In-Tune Ringer]

An interesting feature of this Dean harmonic ringer is the gong
adjustment. As will be seen, the gongs are mounted on posts which are
carried on levers pivoted to the ringer frame. These levers have at
their outer end a curved rack provided with gear teeth adapted to
engage a worm or screw thread mounted on the ringer frame. Obviously,
by turning this worm screw in one direction or the other, the gongs
are moved slightly toward or from the armature or tapper. This affords
a very delicate means of adjusting the gongs, and at the same time one
which has no tendency to work loose or to get out of adjustment.

[Illustration: Fig. 183. Kellogg In-Tune Ringer]

In Fig. 183 is shown a drawing of the "in-tune" harmonic ringer
manufactured by the Kellogg Switchboard and Supply Company. This
differs in no essential respect from that of the Dean Company, except
in the gong adjustment, this latter being affected by a screw passing
through a nut in the gong post, as clearly indicated.

In both the Kellogg and the Dean in-tune ringers, on account of the
comp