the receiver cord, a strain loop is formed as a continuation of the
braided covering of the receiver cord, and this is tied to the
permanent magnet structure, as shown. By making this strain loop
short, it is obvious that whatever pull the cord receives will not be
taken by the cord conductors leading to the binding posts or by the
binding posts or the cord terminals themselves.

A number of other manufacturers have gone even a step further than
this in securing permanency of adjustment between the receiver
diaphragm and pole pieces. They have done this by not depending at all
on the hard rubber shell as a part of the structure, but by enclosing
the magnet coil in a cup of metal upon which the diaphragm is mounted,
so that the permanency of relation between the diaphragm and the pole
pieces is dependent only upon the metallic structure and not at all
upon the less durable shell.

Direct-Current Receiver. Until about the middle of the year 1909, it
was the universal practice to employ permanent magnets for giving the
initial polarization to the magnet cores of telephone receivers. This
is still done, and necessarily so, in receivers employed in connection
with magneto telephones. In common-battery systems, however, where the
direct transmitter current is fed from the central office to the local
stations, it has been found that this current which must flow at any
rate through the line may be made to serve the additional purpose of
energizing the receiver magnets so as to give them the necessary
initial polarity. A type of receiver has come into wide use as a
result, which is commonly called the _direct-current receiver_,
deriving its name from the fact that it employs the direct current
that is flowing in the common-battery line to magnetize the receiver
cores. The Automatic Electric Company, of Chicago, was probably the