Improvements in and relating to Electric Telephone Systems.
Year: 1895

page_text: Date of Application, 12th July, 1895-Accepted, 28th Sept., 1895
COMPLETE SPECIFICATION.
Improvements in and relating to Electric Telephone Systems.
I, ALEXANDER MARR of 9 Repton Street, Manchester in the County of
Lancaster, Electrical Engineer, 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 :-
This invention relates to those systems of electric telephone exchanges in which
any one subscriber may connect his instrument by a switch or other suitable device
to the line of any other subscriber. In these systems as at present arranged the
lines of all the subscribers are led to each instrument where a switch is provided to
put any of them into circuit. In a typical case, described herein and illustrated
berewith, there are four instruments in different rooms of a works or warehouse
and all the lines are led to each instrument. Thus for instance if No. 1 desires to
communicate with No. 2 he moves his switch on to the stud of No. 2 line and
rings up and speaks. When he has finished he moves his switch back to his own
stud. Should he fail to do so no other subscriber can communicate with him.
The objects of my invention are to remove this disadvantage and to enable a
subscriber to be rung up even when he has neglected to restore his switch to his
own stud, and, in addition, to prevent any other subscriber being rung up than the
one the sender has connected himself to. Upon hearing the bell the subscriber rung
up attends to the instrument and as he fails to hear anything through the receiver
naturally looks to his switch, and, finding he has left his switch arm off his home
stud puts it right, when conversation may be carried on.
In a system arranged to embody these improvements each instrument is furnished
with a special ringing key and has attached to its line stud a shunt wire which
passes through the bell without going through the speaking circuit.
The appended diagram illustrates one instrument of a four instrument system,
and will be referred to hereinafter. As will be seen the four lines are brought to
the instrument and are attached to studs a b c d any one of which may have the
switch arm e placed upon it. In this case the instrument is No. 1 of the system
and its own line stud is a to which is attached a shunt wire f which communicates
through the bell with earth.
I have only shewn one instrument in the drawing but this will be sufficient to
explain the invention, as they are all similar and each is provided with a shunt
wire from its own line stud.
which may
g
The ringing key consists of a metallic spring or the like.
be brought
against a movable contact to which is attached but insulated therefrom a spring i.
This spring in the position shewn in the diagram closes a circuit across the two
points j and k. When the key g is pressed it makes contact with and at the
same time moves the spring i away from and opens the circuit j k, thus cutting out
the local bell.
I will suppose for the moment that the instrument illustrated is No. 2 of the
system and that No. 2 wishes to communicate with No. 1 who has however left his
switch upon No. 3 stud. The key g is pressed and the current from the battery m
passes through the communicating wire and the contact h, through the key g and
its connected wire to the switch arm e, thence to the stud a and No. 1 line. The
other pole of the battery is earthed as shewu.
I will now assume the instrument to be No. 1 and that the switch has been left
in contact with No. 3. The current entering along line No. 1 arrives at the stud a

page_text: whence it passes along the shunt wire f, through switches s closed by the telephone
hook, along wire fi, through the bell, through the wires and closed circuit jk, to
the earth terminal where its circuit is completed: The bell is thus rung and the
subscriber finding himself unable to speak looks to his switch and connects it to
his own stud..
:
No other subscriber than the one it is desired to communicate with can be rung
up, no matter where he has left his switch arm, as the wire from each switch
arm in each instrument passes through the bridge of the ringing device to the
telephone hook where the circuit is broken as long as the receiver is on the
hook.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is :-
1. In electric telephone systems of the type described, a shunt wire in each
instrument connected to the home stud and passing through the bell or signalling
device to earth, substantially in the manner and for the purpose hereinbefore set
forth and as illustrated by the accompanying diagram.
2. In an instrument for use in an electric telephone system of the type described,
a ringing device and its attached circuits, operating and arranged substantially as
and for the purpose hereinbefore set forth and as illustrated by the accompanying
diagram.
Dated this 11th day of July A D 1805
W. E. HEYS & SON,
Agents for the Applicant