IMPROVEMENTS IN TELEPHONIC APPARATUS
Year: 1884

page_text: I, DANIEL SINCLAIR, of 13 Royal Exchange Square, Glasgow, in the County
of Lanark, Electrical Engineer, do hereby declare the nature of my said Invention
for "IMPROVEMENTS IN TELEPHONIC APPARATUS," to be as follows:-
In telephonic systems as operated in this country, it is usual to employ a single
wire to connect each subscriber to the central exchange, and in practice when the
exchange operator connects together two subscribers on the system, these sub-
scribers cannot communicate direct with the exchange until again disconnected.
To obviate the inconvenience which results a second wire is in some cases provided
to connect each subscriber direct with the exchange, so that the subscriber may
call the exchange by transmitting a signal over this auxilliary wire when he wishes
to be disconnected from one subscriber and placed in communication with another.
This latter plan is found to operate satisfactorily, but it is attended with the
additional expense of providing and maintaining the call wire.
The object of my Invention is to obtain the advantages of the auxilliary call
wire system with the use of a single wire to serve both for communication directly
with the several subscribers and as a means for communicating with the exchange.
This object I attain by connecting each subscribers wire to the switch board at the
exchange, through a polarised indicator of a kind in common use, suspending a
vibrating arm of metal connected to the subscribers wire, and insulated from the
indicator, between the magnet cores of the indicator, and connecting those cores to
the operator's instrument in the exchange.
I further connect to the subscribers instrument a magneto or other current
generator, which at the option of the subscriber can be employed to transmit
continuous currents or alternating currents, or I employ a magneto and a battery
or separate generator to obtain the two kinds of current. Then by transmitting a
continuous current over his wire, the subscriber throws the vibrating arm over
into contact with one of the magnet cores of his indicator at the exchange, and
thereby closes the circuit through the exchange operator's instrument and rings up
the exchange. The subscriber is then in communication with the exchange operator,
who will place him in communication with any other subscriber he may want, and
replace the vibrating arm to cut off the exchange. When the conversation between
the two subscribers is at an end, either subscriber may, by transmitting a con-

page_text: tinuous current along his wire, ring up the exchange operator, and instruct him to
disconnect or make connection with another subscriber. If, when two subscribers
are connected, the one wishes to call the other by a bell signal, he sends an
alternating current over the wires, which will ring the subscriber's bell, but will
not act on tho vibrating arm to close the circuit through the exchange operator's 5
instrument.
I DANIEL SINCLAIR of 13 Royal Exchange Square Glasgow in the County of
Lanark Electrical Engineer do hereby declare the nature of my invention for
"IMPROVEMENTS IN TELEPHONIC APPARATUS," and in what manner the same is
to be performed to be particularly described and ascertained in and by the following
statement:
In telephonic systems as operated in this country it is usual to employ a single
wire to connect each subscriber to the central exchange and in practice when the
exchange operator connects together two subscribers on the system these sub-
scribers cannot communicate direct with the exchange until again disconnected.
To obviate the inconvenience which results a second wire is in some cases provided
to connect each subscriber direct with the exchange so that the subscriber may
call the exchange by transmitting a signal over this auxilliary wire when he wishes
to be disconnected from one subscriber and placed in communication with another.
This latter plan is found to operate satisfactorily but it is attended with the
additional expense of providing and maintaining the call wire.
The object of my invention is to obtain the advantages of the auxilliary call
wire system with the use of a single wire to serve both for communication directly
with the several subscribers and as a means for communicating with the exchange.
This object I attain by connecting each subscribers wire to the switch board at the
exchange through a polarised indicator of a kind in common uso suspending a
vibrating arm of metal connected to the subscribers wire and insulated from the
indicator between the magnet cores of the indicator and connecting those cores to
the operator's instrumont in the exchange.
I further connect to the subscribers instrument a magneto or other current
generator which at the option of the subscriber can be employed to transmit
continuous currents or alternating currents, or I employ a magneto and a battery
or separate generator to obtain the two kinds of current. Then by transmitting a
continuous current over his wire the subscriber throws the vibrating arm over

page_text: into contact with one of the magnet cores of his indicator at the exchange and
thereby closes the circuit through the exchange operators instrument and rings up.
the exchange. The subscriber is then in communication with the exchange operator
who will place him in communication with any other subscriber he may want and
replace the vibrating arm to cut off the exchange. When the conversation between
the two subscribers is at an end either subscriber may by transmitting a con-
tinuous current along his wire ring up the exchange operator and instruct him to
disconnect or make connection with another subscriber. If when two subscribers
are connected the one wishes to call the other by a bell signal be sends an
alternating current over the wires which will ring the subscribers bell but will not
act on the vibrating arm to close the circuit through the exchange operator's
instrument.
In the accompanying drawings which illustrate a typical modification of the
arrangement I prefer to adopt in carrying out my invention figures 1 and 2 are
Bectional elevations at right angles to each other of a ringing magneto of the kind
ordinarily employed in telephonic systems in use but for the purposes of my invention
specially provided with separate current collectors A and B and connecting wires a
and b to a switch C on the casing of the magneto such switch being in turn con-
nected to the line wire W leading to the indicator at the exchange and to earth.
The one current collector A is in contact with the armature spindle of the magneto
and transmits from it the positive and negative currents alternately generated
while the other collector B is in contact with a commutator on the armature spindle
and transmits currents only of one polarity either positive or negative. It is
obvious that if the switch C be placed in contact with the terminal a¹ of the
wire a connected to the alternating current collector A. alternating currents will be
transmitted through the line wire W to the indicators at the exchange and if the
switch be turned into contact with the terminal b₁ of the wire b from the single or
continuous current collector B continuous currents of one polarity will be trans-
mitted to the indicators at the exchange. To each subscriber's wire at the exchange
I connect (in lieu of the ordinary indicator) a polarised indicator D of any well
known kind as is illustrated in figure 3 the subscribers wire passing round the
cores d of the indicator to the exchange operators telephone, the ordinary switch
board being provided to connect subscribers together.
When a continuous current is transmitted from the magneto by a subscriber
the vibrating arm e of the polarised indicator is attracted to one of the magnetised
and insulated cores d which retains it and the circuit is closed through the core d
to the exchange operator's telephone, with which the cores are connected as
shewn. The exchange operator will thus be called and will place the subscriber
calling in communication with any other subscriber on the system.
When the subscriber transmits an alternating current the vibrating arme of the
indicator D vibrates without making contact or closing the circuit through either
of the cores but the current is transmitted direct to the subscriber to which the
calling subscriber is connected and rings the bell on his instrument.
Instead of employing the magneto with separate collectors and switch as
illustrated the ordinary form of magneto may be used to transmit the alternating
currents through the subscribers line and the polarised indicators and a battery be
employed and connected to the line wire to transmit the contunuous currents.
As an equivalent of the polarised indicator an ordinary indicator may be
employed having a vibrating arm which is kept normally out of contact with the
indicator.
In some exchange systems it is usual in connecting together two subscribers to
cut out the separate indicators in order to lessen the resistance by connecting the
subscribers wires by means of the usual jacks and plugs and a separate wire
passing through a ringing off indicator. In applying my invention in such cases I
employ a polarised indicator in lieu of the ordinary ringing off indicator.
Thus in figure 3 if subscriber N° 1 is to be connected to subscriber N° 3 instead
of plugging the respective jacks J to make the connection through the indicators

page_text: the indicators would be cut out by providing jacks in the subscribers line wires
which would be connected direct (instead of through the indicators) by a separate
wire having in circuit a polarised indicator similar to those shown in figure 3.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I would observe that
I am aware that the objects attained by me have been sought to be attained under
prior patents and especially under the patents N° 1328 A.D. 1882; N° 1059 A.D.
1883; and N° 11843 A.D. 1884. I therefore declare that I make no claim to be
the first to attain those objects otherwise than as described, nor do I claim anything
covered or claimed in the patents above referred to; nor do I claim the construc-
tion of the separate instruments herein described and illustrated which aro well
known and in common use for many purposes but what I do claim as my
invention is
1. The arrangement in a telephone exchange system of a magneto or current
generator or generators in a subscribers office, adapted to transmit alternating or
continuous currents, in combination with a polarised indicator or series of polarised
indicators whose cores are connected to the exchange operator's telephone sub-
stantially as and for the purpose set forth.
2. The employment in a telephone exchange system of a polarised indicator in the
subscriber's circuit the cores of which are connected with the exchange operator's
telephone and whoso vibrating arm is in the subscriber's circuit as and for the
purpose set forth.