Year: 1887

page_text: I, GEORGE FREDERICK REDFERN, of the General Patent Office, No. 4, South Street,
Finsbury, in the county of Middlesex, Patent 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 this invention is the establishment of binary or multiple telephonic
communications simultaneous or not between soveral telephonic stations or subscribers
and the invention consists in novel arrangements of commutators and circuits and the
general arrangement of the exchange for establishing such communications.
In one arrangement the person conducting the central exchange can-Firstly, Call
up each station or subscriber of the system individually and reciprocally receive the
call of each station or subscriber. Secondly-Communicate by telephone either with
each station or subscriber separately or with any number of them simultaneously,
each of the subscribers connected up being then able to take part in the conversation.
-Thirdly Place the several subscribers two and two in independent communication,
without himself taking part in the conversation, the subscribers in communication
being able besides to call up the person at the central exchange in order to inform
him when the conversation is finished.
The accompanying drawings illustrate a telephone exchange apparatus arranged to
communicate with eight telephone stations or subscribers. Similar letters in all the
figures represent similar parts.
Figure 1 is a front elevation of the apparatus with the table on which it is placed;
figure 2 is a plan of the same; figure 3 is a longitudinal section of the apparatus;
figure 4 represents an interior view of the apparatus shewing the arrangement of
wires, the vertical part which carries the coils of the signalling mechanism being
shewn in the same plane as the horizontal part of the apparatus.

page_text: The apparatus contains besides the ordinary parts of a telephonic apparatus the
bell S, the transmitter B, the receivers D, the suspension hook T, the indicators E
(signalling apparatus) and the commutators F.
These various constituent parts of the apparatus are mounted on the cover of a case
made of hard wood; this case is placed between slides on a table Z in the interior of
which are the elements of the local batteries and which serves at the same time as a
writing table; the feet of the table may be turned back underneath.
The parts S B D E may be arranged as shewn or in any other suitable manner.
The arrangement shewn of each of the commutators F, on the contrary is important
and will be described with various details.
The various metallic parts of this commutator connected with the electric circuits
are all arranged on the interior face of the apparatus. The pivot m (figure 3), of
each of them is formed of an insulating material such for example as ivory and is
provided at its outer end with a metal head forming a shoulder and operating knob n,
and at its inner end with a square and a screw and nut whereby it is securely
connected with the needle or pointer a.
At about the middle of its length and on its outer part the insulated pivot is
surrounded with a spiral spring one end of which bears on the hard material of the
case (in a recess which is concentric with the pivot), the other end bearing on the
shoulder of the knob, which it constantly serves to press outwards. The tension of
the spring equalizes the pressure of the interior needle or pointer on its contact pieces
and proper contact is thereby ensured.
8,
The outside operating knob n (figure 2) is provided with an index for indicating on
a dial marked with divisions the stopping position or communications established by
the interior needle or pointer a. Over this needle or pointer is a circular metal
plate M (figures 3 and 4) surrounded by as many brass blocks, insulated from each
other, as there are stations or subscribers in the system with the addition of two
supplementary blocks for the purpose hereinafter described and marked respectively s,
and c.
A part f, of the central plate M diametrically opposite to the blocks
and c,
is cut and separated from and has no direct electrical communication with the plate.
The plate M is formed of three circular portions, the centre portion is of the wholo
thickness of the plate; the middle portion forms an annular recess, and that at the
edge is fluted or undulated with the lower parts opposite each block e; the part f,
is also so formed. This arrangement allows the needle or pointer a, to make contact
with the central part of the plate and at the same time allows the longer arm of the
needle or pointer to bear upon any one of the blocks without touching the fluted
portion.
The shorter arm of the needle or pointer bears upon this latter portion beyond the
periphery of which it does not extend. This arm only acts electrically when it bears
on the block f, that is to say, when the end of the long arm of the needle or pointer
bears on one of the blocks s, or c, (see the position of the needle or pointer in the
commutators Numbers 1 and 6).
The plates K receive the line wires connected at 1, by means of the spring contact
pieces k, when the case is closed. The wire. of each line then leads (from the plate K)
to one of the ends of the signal coil by passing through the part f, of the corre
sponding commutator, (this part f, is therefore connected to the line before the signal
coil). The other end of the signal coil is connected with the plate M of the corre
sponding commutator. The signal coil is thus placed in the way of the line wire
before the latter is connected with the needle or pointer of the commutator by the
central plate.
The plate R¹, is connected by means of spring contact pieces to the block 1, which
communicates with the common return wire.
The plates P and Q with the corresponding spring contact pieces p³, and q', are
connected to the positive and negative poles of the local signal or bell battery; the
plates u, and V, and the corresponding spring contact pieces u¹, and v¹, receive the
current of the microphone battery.

page_text: The commutator T which carries one of the receivers D operates in the manner
usual with apparatuses of this kind.
Having described all the constituent parts of the apparatus I will now explain its
operation and describe the arrangement of the wires which connect the various parts.
For this purpose and to facilitate the description I will explain by way of example
the different cases of communication which may occur.
In the normal state all the indicators b, are raised and the indices of the commu-
tators F, are in the vertical position; each of the contact needles or pointers a, in the
interior of the case is then resting with the end of its longer arm on the upper block
marked with the number of the corresponding station or subscriber of the system.
Supposing now for example subscriber No. 4 rings up the exchange the current will
arrive through the block 1, and will pass through a wire marked
at
the bottom of the case until it reaches the spring contact piece, thence it will pass to
the plate K, from which the wire marked
will conduct it to the
block f; the current then passes along the wire marked
and reaches
and reaches the plate M, it passes through the needle or pointer a*, and through the
wire marked
to the common return wire which communicates with the
the coil d'; it passes through the coil, leaves by the wire marked
plate R
It is to be observed that apart from the fixed spring contact pieces which could if
required be replaced by flexible continuous connections there is for each commu-.
tator F only a single frictional contact piece of which proper working is indispensable
for ensuring the communications.
In passing into the coil d, the current disengages the indicator 6, when it will
take the position represented by the indicator in figure 1; in falling, the indicator 64,
the hinge of which is connected to the negative pole (the zinc) Q of the bell battery,
comes upon the metal plate G and closes the circuit of this local battery. In fact the
current coming from the negative pole Q passes through the wire marked
a,
through the indicator and the plates D having the screws w, and enters the bell coil;
the end of the wire marked
is fixed to the metal plate of the bell
signalling mechanism the current necessary for actuating the trembling bell or the
relay actuating a local bell, as usual, arrives directly at the point i, through
the wire marked
which connects this point i, with the plate P (positive
pole of the local battery). After having understood the call the attendant raises the
indicator 6, and turns the index on the table to the divisions; the position of the
index is indicated in figure 2, for subscriber No. 6; at the same time the needle or
pointer will have the end of its long arm on the block s, figure 4, whilst the other
arm will rest on the block fe-The current leaves at P (positive pole of the bell
battery) reaches the blocks, passes through the needle or pointer and leaves by
the wire marked
which is the line wire communicating with sub-
scriber No. 6, sounds the said subscriber's bell and returns through the return wire
marked
to the negative pole Q of the local battery so as to close the
circuit. In order to commence the conversation, for example to receive the orders
from the station or subscriber of the system the attendant turns the indicator
(figure 2) in a line with the division marked c, as shewn in the drawing for station or
subscriber No. 1, for example; the needle or pointer a (figure 4), will then have the
end of its long arm bearing on the block c¹, whilst its other arm will bear on the
block; the operation will then be as follows: The receiver d, must be unhooked,
the lever t, of the commutator which supports it, drawn by the spiral spring, will bear
on the contact strips g, and h, thereby closing the inductor current of the local
battery of the microphone. The current leaves at u, by the wire marked
arrives at a passes through the induction coil A, leaves at B,
passes through the wire marked
and through the
microphone, passes to the contact spring g, and thence, by means of the contact of the
lever T, to the spring h, and finally passing through the wire marked
returns to the positive pole V of the microphone battery.

page_text: n the same time the inducted current leaves the coil at y, passes to the spring g,
through the lever of the commutator T to the plate O, through the wire marked
and continues through the wire marked
to the block c', traverses the needle or pointer a, and leaves by
the block f¹, thus following the shortest line in the line wire marked
---
and passing through the plate K¹, the spring contact piece and the con-
necting blocks -The current returns through the return wire marked -
passes to the plate Q, traverses successively the two receivers and comes back through
the wire marked
into the coil at 8; the circuit is
then closed as required.
It will be seen by the preceding description that by reason of the arrangement of
the central plate M, with the block f, the coil of the indicator is short circuited by the
contact of the short arm of the needle or pointer with the block f, at the same
moment that the central station calls up the subscriber or speaks with him.
-
Having described the manner of ringing up and communicating with the various
stations or subscribers of the system, supposing now for example, subscriber No. 3
has asked to be put in communication with subscriber No. 8, the attendant at the
exchange in this case has only to turn the indicators on the table figure 2 as shewn
in the drawings for these two stations or subscribers, that is to say, on the dial
corresponding with station No. 3 to place the indicator in a line with the division
marked 8 and on the dial corresponding to station No. 8 to place the indicator in a
line with the division marked 3. The needles or pointers a, in the interior (figure 4)
will have the points of their longer arms bearing at this moment on the blocks e³).
respectively which are connected directly to each other by a wire indicated by thick
dotted lines thus
The end of the other arm of the needles or pointers a,
bear on the plates M³, and M.-The desired communication between subscribers Nos. 3
and 8 will be then established without the attendant of the exchange taking part in
the conversation of the two subscribers as the needles or pointers a, are connected
with the blocks e³, e, during the whole time that the conversation lasts. The passage
of the current in the exchange will be easily understood; it arrives from the station No. 3
for example through the wire marked
and through the spring
contact piece ³, to the plate K³, continues through the wire marked
to the block 3, passes through the wire marked
the coil d³, which it leaves by the wire marked
the central plate M³, passes through the needle or
commutator No. 3 the wire marked
-
to
reaches
pointer a³, the block e, of the
reaches the block ea, of the
commutator No. 8 whence it passes to the needle or pointer a³, and to the central
plate M³, through the wire marked
to the coil de, leaves by
and passes to the block f, and to the station
, passes through the plate K*,
the wire marked
No. 8 through the wire marked
of the spring contact piece 48, and the connecting block .
During the conversation the coils of the indicators of the subscribers in communi-
cation are interposed in series on the telephonic circuit which does not practically
interrupt the communication and allows of the exchange being informed when the
conversation is finished. When the subscribers have hung up their telephones on the
commutator hooks their two apparatuses are connected by a continuous circuit which
includes the two indicators and the two bell mechanisms with or without relays in the
subscribers' apparatuses. If one of the subscribers presses on his ring-off knob, that is
to say, connects his battery instead of his bell in the circuit the bell of the subscriber
with whom he has been speaking will immediately be operated and the current
circulating through the line will release at the same time the two indicators in the
exchange, meanwhile the vibratory and alternate telephonic current will be quite
inoperative.
It should be remarked that in this apparatus the communication of the various
subscribers is effected in each case through a single wire. This arrangement will be
found sufficient whether a second common return wire be connected to the exchange
after being connected to the second wires of several stations or subscribers or the

page_text: second wires of the various subscribers be brought separately to the exchange and
connected together by the binding screw of the common return wire. This latter
arrangement allows of the application of this invention to the systems in which double
wires are employed between the various stations when the exchange is provided with
a single circuit for each subscriber for placing the said subscriber in communication
with the exchange. The conductors of the system connected to this apparatus are in
no way led to earth from which they are always carefully insulated.
The employment of a common return wire is very advantageous because it effects
considerable economy in the system. Nevertheless a double return wire may be
employed, that is to say, each subscriber can be separately connected with the central
station.
Having now particularly described and ascertained the nature of the said invention
and in what manner the same is to be performed I declare that what I claim is :-
1. The central telephone exchange apparatus for establishing binary or multiple
telephonic communications simultaneously or not between several telephone stations
or subscribers the parts of which apparatus can be operated by the attendant in the
exchange and which are arranged entirely or partially in a horizontal position
substantially as herein before described and illustrated in the accompanying drawings.
2. A commutator F, for electric currents of circular form having its pivot insulated
and provided outside with an operating button or knob and with an indicating hand
(figure 2) and inside with the double pointer a (figure 4) having its two arms of
unequal lengths whereby it can be placed in communication simultaneously with
contact makers placed at unequal distances from the centre the constancy of such
communication being insured by a spiral spring and all the metallic parts of the
commutator F, connected with the electric circuits being situated exclusively in the
interior of the apparatus.
3. In a central telephone exchange apparatus the arrangement whereby the coils d
of each annunciator b, are short circuited when its operation is to be interrupted
instead of it being withdrawn from the circuit as is usually done.
Dated this 20th day of Anil 1887