manufactured by the Western Electric Company. In this the bridge of
the original White transmitter is dispensed with, the electrode
chamber being supported by a pressed metal cup _1_, which supports the
chamber as a whole. The electrode cup, instead of being made of a
solid block as in the White instrument, is composed of two portions, a
cylindrical or tubular portion _2_ and a back _3_. The cylindrical
portion is externally screw-threaded so as to engage an internal screw
thread in a flanged opening in the center of the cup _1_. By this
means the electrode chamber is held in place in the cup _1_, and by
the same means the mica washer _4_ is clamped between the flange in
this opening and the tubular portion _2_ of the electrode chamber. The
front electrode is carried, as in the White transmitter, on the mica
washer and is rigidly attached to the center of the diaphragm so as to
partake of the movement thereof. It will be seen, therefore, that this
is essentially a White transmitter, but with a modified mounting for
the electrode chamber.

A feature in this transmitter that is not found in the White
transmitter is that both the front and the rear electrodes, in fact,
the entire working portions of the transmitter, are insulated from the
exposed metal parts of the instrument. This is accomplished by
insulating the diaphragm and the supporting cup _1_ from the
transmitter front. The terminal _5_ on the cup _1_ forms the
electrical connection for the rear electrode, while the terminal _6_,
which is mounted _on_ but insulated _from_ the cup _1_ and is
connected with the front electrode by a thin flexible connecting
strip, forms the electrical connection for the front electrode.

Kellogg Transmitter. The transmitter of the Kellogg Switchboard and
Supply Company, originally developed by Mr. W.W. Dean and modified by