IMPROVEMENTS IN TELEPHONES
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by John Henry Johnson at the Office
of the Commissioners of Patents on the 30th March 1882. A communication
from abroad by Charles Gustave Rodrigues-Pereire of Paris in the Republic
of France.
ور
JOHN HENRY JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman "IMPROVEMENTS IN TELEPHONES A communication from Abroad
by Charles Gustave Rodrigues-Pereire of Paris in the Republic of France
This Invention relates to an improved system of differential telephone acting as
receiver and transmitter and provided with a coil of special construction acted
upon simultaneously by differential currents being also common to the transmitting
microphones and to the receiving telephones:
According to this Invention the armature employed in ordinary telephones is
replaced by a core of soft iron permanently magnetized at both extremities by
two small coils communicating with a battery element:
The said Core constitutes also the core of a large coil occupying the space
between the said two small coils and is supported by brackets fixed to a right
angled frame or support upon which two microphones are also arranged in any
convenient manner
Upon the before mentioned core is coiled an induction wire and upon or over
this induction wire two other wires of different length and diameter are coiled in
succession.
That of the said coils which is nearest the core is connected to one microphone
and the other or outer coil is connected to another microphone.
The said microphones are in communication with two batteries of greater
intensity than the local battery of the before mentioned two small coils at the
ends of the core, these two batteries are of different intensities; for example if the
intensity of the battery of the said small coils is equal to one the intensities of
the batteries of the microphones will amount respectively to three and four:
A telephonic diaphragm is fixed at each end of the core each diaphragm being
enclosed in a case and is capable of being adjusted at a suitable distance from the
poles of the said core.
A stiff tube terminating in a trumpet mouth is attached to each case and in a
convenient position for each car of the operator :-These tubes are secured to the

page_text: respective cases and capable of turning thereon in such a manner that when once
adjusted according to the height or position of the operator they remain in that
position so that the hands are left free while a message is being sent or received:
The apparatus thus arranged being fixed in a room or telephonic office it is
simply necessary to speak in the direction nearest to a line bisecting the right
angle formed by the two boards forming the support of the two microphones:
Differential currents are then produced and the large coil acts in precisely the
same manner as the single wire employed in the harmonic or musical telegraph
that is to say that the communication and the answer pass through the core
without interruption:
The arrangement of this differential telephone may vary as regards both the
form and the details:
For example in place of arranging the two microphone plates as described a
single plate may be employed with two or more microphones arranged before and
behind this plate and in communication with two or more batteries of different
intensity and with the large coil which may be arranged in any convenient position.
By speaking against this plate the same result will be obtained as in the preceding
arrangement.
It would be observed that the system is based upon the simultaneous operation
of two or more microphones of any construction acted upon by Electric currents of
different intensity acting upon the large coil.