Improvements in the Arrangement of Telephone Circuits and in Apparatus therefor.
Year: 1893

page_text: Date of Application, 27th July, 1893-Accepted 2nd Sept., 1893
COMPLETE SPECIFICATION.
Improvements in the Arrangement of Telephone Circuits and in
Apparatus therefor.
1, Sir CHARLES STEWART FORBES, Baronet, 28, Queen's Gate Terrace,
London, S.W., East India Agent, do hereby declare the nature of this invention
and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement :--
The object of my invention is to provide an economical and easily worked
arrangement of telephone circuits whereby the members of a household, hotel, or
other small community of persons may inter-communicate without the disadvantages
incident to a central station and switch board with cost of its attendant for
effecting interchange. My invention is more particularly applicable to telephone
circuits in which the telephone or the telephone and microphone when employed
are in series with the battery but it is also applicable to circuits in which secondary
currents are employed. The way and manner in which my invention is carried into
effect will be readily understood by means of the drawings annexed in which :-
Fig. 1 shews diagrammatically a circuit arranged for 3 stations.
Fig. 2 shews to an enlarged scale the first form of switch board as employed at
station A, for effecting interchange.
Fig. 3 is a cross section of same on line a,
Fig. 4 is a modified form of switch board.
Fig. 5 is a section on line C. D. Fig. 4.
Fig. 6 is a diagrammatic view shewing 3 stations operated upon this system.
Fig. 7 is a front elevation of chain switching gear.
Fig. 8 is a side view of same.
Fig. 9 is a plan.
Fig. 10 is a diagrammatic view shewing 3 stations operated by the chain
switching gear.
Fig. 11 is a diagrammatic view shewing the apparatus employed for operating
telephones upon a secondary or transformed circuit.
Fig. 12 is an elevation of a transformer coil operating telephone upon a closed
circuit.
Figs. 13, 14 are a plan and side elevation of radial switching gear.
In the drawing 1 and 2 represent a going and returning lead or wire between
which at any suitable part is bridged a battery, of sufficient strength to overcome
the resistance of the lead's, instruments and connections employed. Each station,
which is indicated by the uppermost letter A. B. C, is provided preferably with a
micro-telephone instrument T, an independent wire 3, 4, 5, and a switch
board v,, . The switch boards or blocks are constructed as follows:-A. piece
of wood, ebonite or other suitable insulating material E, (see Figs. 2, 3,) is
perforated with a series of holes preferably of oblong shape; they may however
be of any other suitable shape and in these holes are secured by bending over at a right
augle and fastening by screws f, to the board or block, a series of separated metallic
springs. Covering the connections thus provided for, and secured by screws or
the like is an ebonite, wood or metal plate h, upon which is engraved the name of
the various stations connected by the switch board or block. The wires or
conductors connecting the various stations are secured to the metallic springs by
binding screws in the following manner.
nast night hand cuming a unon switch board is connected

page_text: letter A, at the B, and C; stations. The other two right hand springs g¹, y" in the
A station are both connected to the return battery lead 2, the left hand
springs, being connected by wires 4, 5, with springs of similar name or
letter in the B. and C, stations. In the second or B, station the uppermost spring g
on the right hand is connected to the positive wire 1, and springs g, g" marked
respectively A, C, to the negative wire. And in station C, the uppermost right
hand spring, marked C, is connected to the positive wire; 9, representing A, B,
to the negative. At each station the telephone T, is fitted preferably with a
microphone M, and bell with suitable switching connections, one form of which I
have shown in the drawing, the operation of which will be readily understood.
Wires w, w', corresponding to line and return are preferably formed of flexible
strands and terminate in plates p, p, mounted up on either side of an ebonite or
other plug P, and carefully insulated from each other (see Fig. 3). This plug is
so shaped as to fit tightly into the oblong or other shaped hole e, and make good
electrical contact with the divided springs. One of the free ends of the strand ',
is suitably connected to the pivot, of telephone lever, and the other is connected
through the bell terminal to contact t. The operation of this part of my invention
is as follows:-
It is an understood condition between the various users that the plug P,
connecting their own number or letter to line, (see Fig. 1) is always in its place
when the instruments are not in use, the effect of this being to place the wire of
each respective user upon one side only of the battery. If however, station A,
wishes to call up B, he removes his plug from the hole representing his station and
places it in B. The current when the poles of the battery are arranged as shewn
with reference to the leads 1, 2, will therefore flow from the positive lead 1, to
spring and by plate pl on plug P, to wire w, at B, through bell t, causing it to
ring and to bell contact t¹, thence by lever j, and wire w¹, to strip g, entering
station A, by spring, thence by plate p, on plug P, to pivot s, and through
"bell t, causing it to ring and plate to y' and the negative lead; or assuming the
plugs to be replaced and that B, wishes to speak to A, B, removes his plug and
places it in the plug hole marked A. The current now flows from the positive wire
to spring g, at A, and by plate p¹ on plug P, and wire w, to bell, causing it to ring,
thence to pivots, wire w¹, and spring to at B, by plate, wire w pivots,
to bell, returning by g, to the negative wire. By removing the telephone T, or ear
trumpet, replacing it, as shewn, or equivalent receiving device operating the
switch lever, the current passes through the telephone and microphone, or telephone
only as the case may be, and conversation can be carried on. It will be observed
that the plugs P, operating with the divided springs connected to the battery as.
shewn, act as current reversers.
Figs. 4, 5, 6, shew another form of switching device whereby similar results are
obtained. The block E, may be formed of slate, ebonite, wood or other suitable
material and is fitted with a number of circular or other shaped metallic plug holes
corresponding to the number of users. Each separate plug hole el is fitted with a
binding screw, and to these are connected the line wires 3, 4, 5, at each station.
Although the plug holes may be arranged in any order, it is convenient for the
purposes of description that a similar order should be observed to that just
described. At stations A, B, C, each plug hole being denominated by the initial
letter, number or name of the station, is fitted with a metallic spring switch Q,
pivoted at m, and each binding screw k, is connected to its respective line wire. A
spring is attached to a post z, and to the arm of metallic switch Q, and an ebonite
or other insulating plug, is screwed or driven into a hole formed in the side of
switch arm. When the plug P¹ is out of the plug hole e', as shewn in the A, station,
Figs. 4, 6, the switch Q, is drawn by the action of spring s', against the contact p!",
connected as shewn to the positive wire of battery, but when the plug P¹, is
inserted in the hole as at B, C, stations, the flexible tongue of switch Q, is forced
against the contact p" connected to wire 2, and the negative side of battery. In
any convenient position upon the switch block is mounted a plate or terminal n, and

page_text: from this is led a flexible wire wll terminating in metallic plug P₁, while another
wire wis led from it to the pivots, of telephone switch lever j, this, as shewn at
all the stations, rests against the bell contact t', but when the lever j, is raised by
removing the telephone T. ear trumpet or the like operating the same from the
hook, this wire is placed in contact with the telephone terminal T', and speech can
be carried on.
The operation of this modification of my invention is as follows:- -When all the
plugs P, are in the first plug hole A, B, or C, at their respective stations, the
spring tongue Q, is forced against contact p" connecting it with the negative side
of battery common to all the users, all the stations being thus placed on one side of
it. If A, wishes to speak to B, he removes his plug and places it in that marked B,
at his station, (as see diagram, Fig. 6,) the spring tongue Q, at A, is now by the
action of spring a', forced against the contact, connected to the positive wire of
battery C. A current will consequently flow from the battery through contact p
to spring tongue Q, and through the bell t, at A, to pivots, thence by plug Pand
wire 4, to the plug hole at B, by plug P1, at that station, to n, returning in the
switch tongue Q, to wire 2, and thus completing the circuit.
I am also able to effect communication between the users, by means of the
apparatus shewn and described in Figs. 7, 8, 9, 10. This consists of a slack
metallic chain wire or equivalent flexible device 6, fastened at one end to a post 7,
secured to the base E, which may consist of fibre, vulcanite, wood or other suitable
substance and at its other end by a screwed pin and nut 8, passing through a hole
in bracket 10, which serves to tighten the chain or wire. At suitable points along
the chain 6, are mounted rollers 11, pivoted in metallic brackets 12, fastened to
the base, and between these rollers, pivoted to a hinge 9, common to them all,
are a series of metallic keys 13. At a convenient point in each key is mounted a
transverse pin 14, insulated by being driven through a plug of ebonite or fibre 15.
This pin, which should consist of silver, platinum or other uncorrodible metal,
engages on one side when in the upward position with a bracket carrying a
contact 16, connected to the + or positive pole of battery and when in the down-
ward position with a contact. 16' connected to the zine or pole. On the other
side of the key the pin engages with a spring 17, connected to the return wire.
Upon the underside of each of the keys 13, towards the front is a contact of copper
or other good conducting metal 18, which engages with a divided spring 19, con-
nected to the station wires 3, 4, 5. It is to be understood that the object of the
slack chain is to prevent the putting down by inadvertence of more than one key
at a time; as will be seen in Fig. 7, the C, key at station A, is depressed and
since by this or equivalent depression of any other key the chain or wire is pulled
tight all the other keys are raised and maintained in the upward position. To
prevent short circuiting an ebonite strip 20, is pinned on the underside of each key,
at the point in which it engages with the metallic chain 6. The operation of this
modification of my invention is as follows (see Fig. 10). It is necessary that the
key 13, representing the distinguishing letter of each station be alway depressed
when the instrument is inoperative. In the case shewn I have assumed that A,
wishes to speak to C. To do this he depresses the key marked C, the chain being
thereby pulled taut raises key A. The current from battery a, will now flow
through contact 16, at A, station, to the insulated pin 14, thence to spring 17,
through bell t, at A, causing same to ring, thence by lever j, and pivot 8, to hinge 9,
along the depressed key C, through spring 19, to line 5, connecting C, through
spring 19 at C, along key marked C, and hinge 9, to bell t, ringing same and
by spring 17, through insulated pin 14, and bottom contact 16' to pole of
battery.
-
Similar results may be obtained by means of the radial form of switch shewn in
Figs. 13, 14, wherein a lever P", is hinged upon a revolving bearing 28, mounted
upon a block of insulating material E. The lever is depressed upon the line
contact plates e" by a spring ". X, is the battery common to the users and
p", pare the contacts connected thereto, between which is mounted upon

page_text: bracket m' the flexible contact Q. In order to prevent the bells upon the various
line circuits from ringing, the lever P is hinged so that by slightly pressing upon
the handle the point may be raised while passing over the contact plates between
its position when at rest, and the plates connected to the station to be called'; a
plug, of insulating material is driven into the end of lever P" as shewn. The
operation of this device being as follows:-When the radial lever P" covers the
initial or station contacts, the plug, forces contact Q, against the contact p" of
battery, and all the stations are on this side of it. If, however, any of the
levers P be moved so as to cover the plate connected to any other number or
letter the other pole of the battery is switched into line by the re-action of
flexible contact Q, thus causing the bell to ring and permitting conversation to be
carried on.
-
In some cases it may be convenient to employ a secondary current for communi-
cating with stables or other offices at a distance (see Fig. 11). To effect this I
include at any one of the stations selected an ordinary induction coil, the primary
wire of which, is in series with the line circuit; 21 is the bobbin, 22 the primary
wire placed in the line circuit and surrounding the soft iron core 23, the
secondary wire 24, is connected through an ordinary magneto machine and bell 25,
at the station end, and to earth plate E, and at the distant end S, to an ordinary
magneto ringing switch having an insulated attachment 26, of the well known form
for closing the microphone circuit contacts 27, and ringing. Assuming the station
at which the induction coil is shewn to be C, station A, or B, can by either of the
previously described switching devices, call up C, by means of the micro-telephone
series apparatus and instruct him to ring up S, by the magneto apparatus 25.
Since the line wire from A, or B, is joined in series with the primary wire 22, upon
the bobbin 21, the microphonic variation of the current from any station will be
inductively reproduced in the secondary wire 24, and the telephone T, at station S,
included in this separate circuit, when the instrument is removed from the switch
lever j, as well as in the series telephone T, at C; and provided the ratio of the
primary and secondary wires of induction coil be suitably adjusted.so as to produce
the required transformation, S can reply by the inductive re-action of the
secondary 24, upon the primary wire 22, which with the telephone T is in the series
circuit at C, when the microphone M, at S, is switched in and operated in the usual
manner. If preferred and with a view to economise the E.M.E., of battery
current which as is well known must be greater in a circuit in which the resistance
of two telephones and microphones with battery have to be overcome, than in a
simple primary circuit the telephones in which are actuated by an induced current,
I may arrange the telephones at all or any of the stations in the manner shewn in
Fig. 12, in which the primary of the induction coil is included in the line circuit in
the manner described and the secondary closed upon itself through the telephone.
As is well understood an induction coil can be so wound as to give any required
degree of transformation provided the resistance of the separate circuits are
known.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
CLAIMS.
1. The improved circuit arrangement for telephones operated by the switching
apparatus herein shewn and in the way and manner described.
2. The combination of the current reversing devices with a battery or other
source of electricity common to all the users as herein set forth whereby any
subscriber is enabled to place himself in communication with any other subscriber
by the means, and in the way and manner described.
3. The combination in or with telephone circuits of the particular arrangement
of plug block E, and the divided springs therein one of which, preferably the upper-
most, communicates with the + pole of the common battery, the remainder on the

page_text: -
same side with the
pole, while the opposite springs connect by a separate wire
the corresponding letter in each station. The plug P, having insulated plates p, pl
flexibly connected to line and return, and so arranged as that when in the upper-
most plug hole in each station, said stations are cut out, but when placed in any
other plug hole, communication is effected by a current of varying direction
substantially as described with reference to Figs. 1, 2, 3.
4. The combination in or with a telephone circuit or circuits, of a single plug P¹
which when placed in the plug hole e', to which the separate line wires 3, 4, 5, arc
connected reverses the position of the switch tongue Q, with regard to the common
battery contacts p p thereby altering the direction of the current flowing
from said battery through the closed telephone line circuit, substantially as shewn
in Figs. 4, 5, 6.
5. The combination in or with a telephone circuit of the particular apparatus
described under Figs. 7, 8, 9, 10 for switching purposes between subscribers.
6. In switching devices for effecting telephonic communication between subscribers
the use and employment of the chain 6, so operated by the keys 13, as that
depressing any one key raises that previously depressed, the battery contacts 16, 16'
and the insulated pin 14, engaging therewith and with the return current spring 17,
for the purposes set forth.
7. The combination in or with a series telephone circuit operated by reversed
currents by the means, and in the manner described of the transformer coil 21,
whereby the telephone T, is operated on metallically closed or earth circuit in the
way and manner set forth.
8. The combination in or with a series telephone circuit, of the particular form
of radial switching device shewn in Figs. 13, 14, for effecting interchange between
the subscribers in the way and manner set forth.
FRANCIS M. ROGERS,
Agent.