nd
condensers. All of these will be seen in the diagram (Fig. 8). It
will be understood, of course, that the polar relay, as used in the
quadruplex system, is wound differentially, and therefore its operation
is somewhat similar in principle to that of the differentially wound
neutral relay, in that it does not respond to the operation of the key
at the home office, but only operates in response to the movements of
the distant key.

Our explanation has merely aimed to show the underlying phenomena and
principles in broad outline without entering into more detail than was
deemed absolutely necessary. It should be stated, however, that between
the outline and the filling in of the details there was an enormous
amount of hard work, study, patient plodding, and endless experiments
before Edison finally perfected his quadruplex system in the year 1874.

If it were attempted to offer here a detailed explanation of the varied
and numerous operations of the quadruplex, this article would assume the
proportions of a treatise. An idea of their complexity may be gathered
from the following, which is quoted from American Telegraphy and
Encyclopedia of the Telegraph, by William Maver, Jr.:

"It may well be doubted whether in the whole range of applied
electricity there occur such beautiful combinations, so quickly made,
broken up, and others reformed, as in the operation of the Edison
quadruplex. For example, it is quite demonstrable that during the making
of a simple dash of the Morse alphabet by the neutral relay at the home
station the distant pole-changer may reverse its battery several times;
the home pole-changer may do likewise, and the home transmitter may
increase and decrease the electromotive force of the home battery
repeatedly. Simultaneously, and, of course, as a consequence of the
foregoing actions, the home neutral relay itself may have had its
magnetism reversed several times, and the SIGNAL, that is, the dash,
will have been made, partly by the home battery, partly by the distant
and home batteries combined, partly by current on the main line, partly
by current on the artificial line, partly by the main-line 'static'
current, partly by the condenser static current, and yet, on a
well-adjusted circuit the dash will have been produced on the quadruplex
sounder as clearly as any dash on an ordinary single-wire sounder."

We present a diagrammatic illustration of the Edison quadruplex, battery
key system, in Fig.