ith the disk _3_ only during that portion of the revolution while
positive current is being generated, the generator will produce
positive pulsations of current, all the negative ones being cut out.
If, on the other hand, the spring _5_ may be made to bear on the
opposite side of the disk, then it is evident that the positive
impulses would all be cut out and the generator would develop only
negative impulses. Such a generator is termed a "direct-current"
generator or a "pulsating-current" generator.

The symbols for magneto or hand generators usually embody a simplified
side view, showing the crank and the gears on one side and the
shunting or other switching device on the other. Thus in Fig. 78 are
shown three such symbols, differing from each other only in the
details of the switching device. The one at the left shows the simple
shunt, adapted to short-circuit the generator at all times save when
it is in operation. The one in the center shows the cut-in, of which
another form is described in connection with Fig. 75; while the symbol
at the right of Fig. 78 is of the make-and-break device, discussed in
connection with Fig. 76. In such diagrammatic representations of
generators it is usual to somewhat exaggerate the size of the
switching springs, in order to make clear their action in respect to
the circuit connections in which the generator is used.

Polarized Ringer. The polarized bell or ringer is, as has been
stated, the device which is adapted to respond to the currents sent
out by the magneto generator. In order that the alternately opposite
currents may cause the armature to move alternately in opposite
directions, these bells are polarized, _i.e._, given a definite
magnetic set, so to speak; so the effect of the currents in the coils
is not to create magnetism in normally neutral iron, but rather to
alter the magnetism in iron already magnetized.

_Western Electric Ringer._ A typical form of polarized bell is shown
in Fig. 79, this being the standard bell or ringer of the Western
Electric Company. The two electromagnets are mounted side by side, as
shown, by attaching their cores to a yoke piece _1_ of soft iron. This
yoke piece also carries the standards _2_ upon which the gongs are
mounted. The method of mounting is such that the standards may be
adjusted slightly so as to bring the gongs closer _to_ or farther
_from_, the tapper.

The soft iron yoke piece _1_ also carries two brass posts _3_ which,
in