ct-current type and employs but a single cylindrical bobbin of
wire. The core of this bobbin and the return path for the magnetic
lines of force set up in it are composed of soft iron punchings of
substantially =E= shape. These punchings are laid together so as to
form a laminated soft-iron field, the limbs of which are about square
in cross-section. The coil is wound on the center portion of this _E_
as a core, the core being, as stated, approximately square in
cross-section. The general form of magnetic circuit in this instrument
is therefore similar to that of the Automatic Electric Company's
receiver, shown in Figs. 52 and 53, but the core is laminated instead
of being solid as in that instrument.

[Illustration: Fig. 55. Dean Steel Shell Receiver]

The most unusual feature of this Dean receiver is that the use of hard
rubber or composition does not enter into the formation of the shell,
but instead a shell composed entirely of steel stampings has been
substituted therefor. The main portion of this shell is the barrel
_1_. Great skill has evidently been exercised in the forming of this
by the cold-drawn process, it presenting neither seams nor welds. The
ear piece _2_ is also formed of steel of about the same gauge as the
barrel _1_. Instead of screw-threading the steel parts, so that they
would directly engage each other, the ingenious device has been
employed of swaging a brass ring _3_ in the barrel portion and a
similar brass ring _4_ in the ear cap portion, these two being slotted
and keyed, as shown at _8_, so as to prevent their turning in their
respective seats. The ring _3_ is provided with an external screw
thread and the ring _4_ with an internal screw thread, so that the
receiver cap is screwed on to the barrel in the same way as in the
ordinary rubber shell. By the employment of these brass screw-threaded
rings, the rusting together of the parts so that they could not be
separated when required--a difficulty heretofore encountered in steel
construction of similar parts--has been remedied.

[Illustration: Fig. 56. Working Parts of Dean Receiver]

The entire working parts of this receiver are contained within the cup
_5_, the edge of which is flanged outwardly to afford a seat for the
diaphragm. The diaphragm is locked in place on the shell by a
screw-threaded ring _6_, as is clearly indicated. A ring _7_ of
insulating material is seated within the enlarged portion of the
barrel _1_, and against this