As is to be expected from any two-pole alternating generator, there is
one cycle of current for each revolution of the armature. Under
ordinary conditions a person is able to turn the generator handle at
the rate of about two hundred revolutions a minute, and as the ratio
of gearing is about five to one, this results in about one thousand
revolutions per minute of the generator, and, therefore, in a
current of about one thousand cycles per minute, this varying
widely according to the person who is doing the turning.

[Illustration: HOWARD OFFICE OF HOME TELEPHONE COMPANY, SAN FRANCISCO
An All-Concrete Building Serving the District South of
Market Street.]

The end plates which support the bearings for the armature are usually
extended upwardly, as shown in Fig. 72, so as to afford bearings for
the crank shaft. The crank shaft carries a large spur gear which
meshes with a pinion in the end of the armature shaft, so that the
user may cause the armature to revolve rapidly. The construction shown
in Fig. 72 is typical of that of a modern magneto generator, it being
understood that the permanent magnets are removed for clearness of
illustration.

Fig. 73 is a view of a completely assembled generator such as is used
for service requiring a comparatively heavy output. Other types of
generators having two, three, or four permanent magnets instead of
five, as shown in this figure, are also standard.

[Illustration: Fig. 73. Five-Bar Generator]

Referring again to Fig. 69, it will be remembered that one end of the