st
entirely eliminated, not by the employment of remedial devices, such
as those often proposed for stirring up the carbon, but by preventing
the trouble by the design and manufacture of the instruments in such
forms that they will not be subject to the evil.

Carrying Capacity. Obviously, the power of a transmitter is
dependent on the amount of current that it may carry, as well as on
the amount of variation that it may make in the resistance of the path
through it. Granular carbon transmitters are capable of carrying much
heavier current than the old Blake or other single or multiple
electrode types. If forced to carry too much current, however, the
same frying or sizzling sound is noticeable as in the earlier types.
This is due to the heating of the electrodes and to small arcs that
occur between the electrodes and the granules.

One way to increase the current-carrying capacity of a transmitter is
to increase the area of its electrodes, but a limit is soon reached in
this direction owing to the increased inertia of the moving electrode,
which necessarily comes with its larger size.

The carrying capacity of transmitters may also be increased by
providing special means for carrying away the heat generated in the
variable-resistance medium. Several schemes have been proposed for
this. One is to employ unusually heavy metal for the electrode
chamber, and this practice is best exemplified in the White solid-back
instrument. It has also been proposed by others to water-jacket the
electrode chamber, and also to keep it cool by placing it in close
proximity to the relatively cool joints of a thermopile. Neither of
these two latter schemes seems to be warranted in ordinary commercial
practice.

Sensitiveness. In all the transmitters so far discussed damping
springs of one form or another have been employed to reduce the
sensitiveness of the instrument. For ordinary commercial use too great
a degree of sensitiveness is a fault, as has already been pointed out.
There are, however, certain adaptations of the telephone transmitter
which make a maximum degree of sensitiveness desirable. One of these
adaptations is found in the telephone equipments for assisting
partially deaf people to hear. In these the transmitter is carried on
some portion of the body of the deaf person, the receiver is strapped
or otherwise held at his ear, and a battery for furnishing the current
is carried in his pocket. It is not feasible, for this s