IMPROVEMENTS IN APPARATUS FOR CONTROLLING TELEPHONIC COMMUNICATIONS
Year: 1881

page_text: LETTERS PATENT to John Imray, of No. 28, Southampton Buildings, Chancery
Lane, in the County of Middlesex, for an Invention of "IMPROVEMENTS IN
APPARATUS FOR CONTROLLING TELEPHONIC COMMUNICATIONS." A commu-
nication from abroad by Leon Alexandre Brasseur and Octave Dejaer, both of
PROVISIONAL SPECIFICATION left by the said John Imray at the Office
of the Commissioners of Patents on the 23rd July 1881.
JOHN IMRAY, of No. 28, Southampton Buildings, Chancery Lane, in the County
of Middlesex. "IMPROVEMENTS IN APPARATUS FOR CONTROLLING TELEPHONIC
COMMUNICATIONS." [A communication from abroad by Leon Alexandre Brassour
and Octave Dejaer, both of Brussels, in the Kingdom of Belgium.]
This Invention has for its object to simplify operations at the central stations of
telephonic systems, to provide against the evils resulting from induction on the
line wires, and to secure secrecy of communication.
For this purpose a distributing tablet is employed in connection with the
commutators, and a special mode is adopted of coiling the two line and return
wires on the receiving and transinitting bobbins whereby induction is prevented,
and the total resistance of the circuit is greatly reduced. There is also applied to
the distributing tablets and commutators an arrangement for secrecy, hereafter
described, and a changeable key is used for making connection; this key consisting
of two parts insulated from each other for exposed lines, and of three parts for
buried lines.
The distributing tablet presents a number of what may be termed key holes,
one for each subscriber. When the attendant at the tablet receives a signal from
a subscriber A that he desires to communicate with another, the attendant intro-
duces the key into the key hole belonging to A, and by turning the key disconnects
the signal. The attendant at the commutator does the same, and communicating
with A ascertains that he desires to communicate with B, he informs the attendant

page_text: at the distributing tablet, who by inserting a second key into the key bole
belonging to B and turning it puts B in communication with A. The key employed
consists of a shank on which are fixed insulated pieces of metal, which on the key
being turned one quarter round are brought to bear against lateral springs fixed
on an ebonite casing of the key, these springs communicating by insulated wires
bundled together and covered so as to form a flexible cord, which wires commu-
nicate with the line, and return, and the battery. The key cannot be withdrawn
without turning it back, and this act puts the two subscribers in communication
with the current of the central office:
In order to ensure secrecy of communication interrupters are employed to
subdivide the line arranged in zig-zag which has to convey the currents of the two
communicating subscribers. The act of putting them in communication breaks
connection with the central office and any attempt to make connection with the
central office or other post, automatically disconnects the two communicants, and
by means of a current from the central station apprises them of the interruption.
The subscriber A by a first current learns that his communication with the central
office is broken, and by a second current that he is put in communication with B,
who on his part knows that he is in communication with A.
In order to prevent the prejudicial effects of induction and to reduce resistance
the instruments having two wires have combined with them induction bobbins
consisting of one inducing and two induced coils.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Imray in the Great Seal Patent Office on the 23rd January
1882.
"
JOHN IMRAY, of No. 28, Southampton Buildings, Chancery Lane, in the County
of Middlesex. IMPROVEMENTS IN APPARATUS FOR CONTROLLING TELEPHONIC
COMMUNICATIONS."' A communication from abroad by Leon Alexandre Brasseur
and Octave Dejaer, both of Brussels, in the Kingdom of Belgium.
This Invention has for its object to simplify operations at the central stations of
telephonic systems, to provide against the evils resulting from induction on the
line wires, and to secure secrecy of communication.
For this purpose a distributing tablet is employed in connection with the com-
mutators, and a special mode is adopted of coiling the two line and return wires on
the receiving and transmitting bobbins, whereby induction is prevented, and the
total resistance of the circuit is greatly reduced. There is also applied to the
distributing tablets and commutators an arrangement for secrecy hereafter
described, and a changeable key is used for making connection; this key consisting
of two parts insulated from each other for exposed lines, and of three parts for
buried lines.
The distributing tablet presents a number of what may be termed key holes,
one for each subscriber. When the attendant at the tablet receives a signal from a
subscriber A that he desires to communicate with another, the attendant introduces
the key into the key hole belonging to A and by turning the key disconnects the
signal. The attendant at the commutator does the same, and communicating
with A ascertains that he desires to communicate with B, he informs the attendant
at the distributing tablet, who by inserting a second key into the key hole belonging
to B, and turning it puts B in communication with A. The key employed
consists of a shank on which are fixed insulated pieces of metal, which on the key
being turned one quarter round are brought to bear against lateral springs fixed
on an ebonite casing of the key, these springs communicating by insulated wires
bundled together and covered so as to form a flexible cord, which wires communicate
with the line, and return, and the battery. The key cannot be withdrawn without
turning it back, and this act puts the two subscribers in communication with the
current of the central office.
In order to insure secrecy of cammunication, interrupters are employed to sub-
divide the line arranged in zig-zag, which has to convey the currents of the two
communicating subscribers. The act of putting them in communication breaks
connection with the central office, and any attempt to make connection with the
central office or other post automatically disconnects the two communicants, and
by means of a current from the central station apprises them of the interruption.
The subscriber A by a first current learns that his communication with the central
office is broken, and bý a second current that he is put in communication with B,
who on his part knows that he is in communication with A.
In order to prevent the prejudicial effects of induction and to reduce resistance,
the instruments having two wires have combined with them induction bobbins,
consisting of one inducing and two induced coils.
Fig. 1, Sheet I. of the Drawings, shews a diagram of the central station and
instruments of the two subscribers that are to be put in communication with each
other, arranged according to the above described Invention.
Fig. 2, Sheet I., shews an inside view and section on A, B, of the improved
distributor in full size.
Fig. 3, Sheet I., shews in several views the changeable key employed.
Fig. 1, Sheet II, shews to a larger scale the commutator for the distributor in'

page_text: three different conditions, namely, that for communication between subscribers,
that of calling, and that of waiting.
Fig. 2, Sheet II., shews the improved system of interrupting commutator with
zig-zag circuits, so as to insure the secrecy of the communications; Fig. 3,
Sheet II., shews an arrangement with a single wire for neutralising the effects of
induction.
In Fig. 1, Sheet I., the full line indicate the line wire, and the dotted line the
return wire; R, R¹, are the receivers; T and T¹ are the induction bobbins of the
transmitters with two induced and one inducing wires; M, M', are the manipulators
or levers with rollers communicating with the springs V, VI, during their
movement; P, P¹, are the batteries.
Central Instrument.-S is the distributor; U, U¹, are the indicators; I., II., III.,
are the interrupting commutators; G are the changeable keys; Q is the battery;
X, X, earth; N, N, telephone and induction bobbin.
In the distributor Fig. 2, a is the tablet of wood or other material; b, a plate
of metal fixed on the outer side of the tablet; c and c are springs or levers
that receive the two line and return wires; d, metal button or plate con-
necting the two line and return wires with the "wait," which connection ceases
on introducing the changeable key into the opening. In the changeable key Fig. 3,
fis the body; g, g, are the insulated studs; h, h, are the springs or levers fixed on
the ebonite J, J'; i is a metal plate separating the ebonite blocks, and communi-
cating with the battery Q of the central instrument; k is a flexible tube of wire
gauze or other material enclosing the line, return, and battery wires; l, l, are the
plates communicating with the springs or levers c, c¹, Fig. 2; m is the insulating
material.
The changeable key being once inserted cannot be withdrawn without being
turned backwards; in this case both the subscribers receive the current from the
central station.
The apparatus operates as follows:-The subscriber Y who demands communi-
cation, causes the disc U¹ of the central station to drop; this signal being given
the attendant in front of the distributing tablet places in the opening of the
instrument Y one of the changeable keys of the commutator III., which in
extending the two wires disengages the disc from this commutator in turning the
key. The attendant for the direct communications who is situated in front of the
commutators does the same, and is then in communication with the subscriber Y
by means of the levers x, x¹, of the second key, combined with the first of the
commutators-III-This attendant-indicates-to-the-operator-of-the-distributor the
number called (Z), and after receiving the reply puts the latter in communication
with the subscriber Z by the simple movement of the second key.
The arrangement for neutralising the effects of induction will be readily under-
stood on reference to ends of Fig. 1, which shew the two instruments. These
instruments, which may be of any known system, are indicated by their bobbins
R, R, for their receivers and T, T₁, for the transmitters. It will be seen that the
bobbins instead of having only one coil are surrounded by two parallel coils, one
of which is formed by the line wire while the other is formed by the return wire.
The induced currents that may be produced through the influence of currents
passing through an adjoining circuit will traverse the two coils in contrary
The same
directions, and will consequently completely neutralise each other.
result may also be obtained by a single wire, that is to say, without a return wire.
This arrangement is shewn at Fig. 3, Sheet II., which represents two instruments
A and B. Two wires n, n, are wound on the bobbin of the receiver and com-
municate with the condenser o at the point o¹. A resistance p is connected to the
wire of the bobbin and with earth t; is a line connected with one of the wires of
the bobbin.
With this arrangement the condenser is only influenced by currents of high
tension, while the weak currents or ordinary induction currents caused by the
vicinity of other line wires arrive, for instance, at a circulate round the bobbin in

page_text: turning to their right till the point o¹, and return in turning to the left (their
tension not being sufficient to influence the condenser o) and pass to earth through
the resistance p.
The arrangement for insuring secrecy of communications consists in dividing by
means of interrupters a metal circuit bent in zig-zag form through which the
signals from the two instruments put in communication have to pass.
This arrangement offers the following advantages:-
1. All communication of the central office with the circuit of the two connected
instruments is interrupted by the fact of their being put in communication.
2. All attempt to put in communication with this circuit either the central
office or another instrument results in interrupting automatically the communication
between the said two instruments.
3. Notice of this interruption will be conveyed automatically to the two
instruments by means of the key to be presently described, which cannot operate
without having previously sent into the circuit a current from the battery of the
central station, which current gives the notice to the two instruments.
4. Lastly, this arrangement offers the advantage that the current of the central
station battery will serve to indicate also the moment when the direct communication
is established between the two instruments.
Thus the calling subscriber will know on receiving the first current that he is
isolated from the central station, and the reception of the second current will
indicate to him that he is connected with the answering subscriber. The latter in
his turn will know on receiving a current that he is connected to the calling
subscriber. Any subsequent current will indicate the interruption of the existing
communication.
Fig. 2, Sheet II., shews a commutator composed of four circuits for grouping at
the same time eight wires, two by two, by means of two keys to each group, in
such manner that interruption will be effected if a third key be introduced between
the two first, and isolation if this third key is situated in the division of the
unoccupied circuit.
The receiver of the central station is isolated as long as the direct communication
lasta

page_text: The electrical communication of the 4 circuits is shewn by full lines, and those
of the 8 line wires by a dotted line.
Having thus described the nature of this Invention, and in what manner the
same is to be performed, as communicated to me by my foreign correspondents, I
claim,―-
First. The herein described arrangement of distributing commutator with
provision of means for neutralising the effect of induction and for insuring the
secrecy of the communications.
Second. The herein described distributing tablet in combination with the
interrupting commutators.
Third. The method of neutralising induction in the bobbins of telephonic
transmitters and receivers by causing the operating currents to pass simultaneously
in contrary directions through two coils wound. in the same direction upon the
bobbin, substantially as herein described.
Fourth. The use in telephonic apparatus of a turning key, constructed and
operating as herein described.
Fifth. The herein described method of connecting the different instruments of a
commutator by means of a circuit bent into zig-zag form, and provided with
interrupters whether applied to a single or a double wire, the interrupting springs
being doubled in the latter case.
In witness whereof, I, the said John Imray, have hereunto set my hand
and seal, this Twentieth day of January, in the year of our Lord One
thousand eight hundred and eighty-two.