, 1889-05-15

that the telephone wire Is perfectly lnSu.
lated from the telegraph wires. These
noises are known as induction noises, and
it was while investigating the phenomena
of 'indu ction with the view of deviSing
means to ObviatQ it's effects in telephones
that Mr.. Langdon-Davies made the dis
covery which has led to the important re-
suits under consideration. His iuvestiga.
tions led him to the conclusion that in.
ductiOn Was caused by some form Of
electrical force, which might be separated
FROM currents and which would pass free
~ through installations impossible by cur
rents. He further concluded thar, If this
we're so, a new series Of Instruments might
be constructed for the utilization of this
force, and capable OF being put III opera
ton in company with current Instruments
on the same wire. HIS conclusions have
been proved to be perfectly correct by
what has since resulted from the develop
mefit of the principle. Instruments have
been made which represent IL system of
communicable of the highest practical
utility, and by means of which Mr.. Lang.
dOn-DAvieS has added u distinct and in
dependent chapter to the history of cleo
trical development. The only form of
electrical force which fndS free passage
through these instruments appears to be
always capable of being associated with
sound. The inventor has therefore de-
nominated the force 'phOnOp0ric impulse"
and the instrument "the phOnOp0re."
1t is certainly very remarkable, and to
some it may appear almost Incredible,
that phonOpOric messages can be- trans
mitted ard received through an ordinary
line wire by the phOnOpore, while at the
same tim. Geographic messages are being
transmitted aud received through the
sano wire by the ordinary Geographic
AppArItuA. No less remarkable is it, but
1t is no less u fact, that the DhOnop0ri0
tnAtrum'ntS have no conducting circuit
through them. The phOnOpOre gives m,
Interrupted passage TO electrical effects
capable OF being associated with sound,
Althengh it does not permit the pISSag 70
Of electric currents. Externally the pho
nOpnric l%ranSmitter resembles an Orlin4,
~, Morse key, IN Duntrd on Il base ahOut
4in. high, containing all inStru ment some
what HlInl Ar TO an induction coil. ThA
impulses are generated in u specially con.
Rtru:trd primary circuit, over which is
wnnnd, in place Of % secondary circuit, u
PnOnO pore consisting Of twD wires, insa.
lated from each other throughout their
whole length aul ~ both ends. b lch If
these wires, however, is connected at one
end to the line. The number OF pin DnOpDric
impulses generated per second lnthe trans
mitter is regulated by the Vibrations Of an
organ reed placed in the primary circuit.
Another reed tuned 10 the same rate of vi
bration is placed as II receiver at the dis.
tant station, III front Of an electro-mag.
net, and the ph0nopOric impulses from the
t%ranslnitter cause it to vibrate. A special
form Of contact breaker, operated by the
receiver reed, completes a local relay cir.
cult when the reed iS still, but breaks it
whenever the r, ed vibrateS at it's proper
rate, thereby setting in actionany required
instrument in connection with any battery.
Divested Of its technical surroundings the
phonOpOre presents itself as q small and
simple apparatus, consisting only of q pair
OF insulated copper wires.
We now turn to its practical application,
and to make this clear we will suppose
that an ordinary telegraph line from one
town to another is provided at each end
with the usual telegraph instruments, and
that, owing to increase of business, it be-
comes'necessary to provide some additional
means of communication. All that is now
necessary is to attach to the line at each
end a phonOpOre, without in any way al
tering the existing Instruments, batteries,
or line. The %phonOpore can be worked at
the same time as the ordinary telegraph
instruments, and one line is thus made to
do the work of two. If the line is already
duplexed. by ordinary duplex telegraph
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