Improvements in or relating to Telephone Installations.
Year: 1898

page_text: Date of Application, 14th June, 1898-Accepted, 14th June, 1899
COMPLETE SPECIFICATION.
Improvements in or relating to Telephone Installations.
I, JOAQUIN LLORENTE LARA, of Cordova, in the Kingdom of Spain, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:-
-
One of the most important of the many forms of electrical apparatus is
undoubtedly the telephone, enabling the human voice to be transmitted instan
taneously from one distant point to another. If the telephone is not in such
general use as it ought to be, a chief reason is that it requires additional apparatus,
the improvement of which has not kept pace with that of the telephone, and which
increases its cost and makes its use complicated.
All telephones at present in use require a call bell battery or a small dynamo
generating sufficient electro-motive force to overcome the resistance of the line
and the winding of the bell.
Even persons unacquainted with the construction of telephones know that
most of the interruptions are chiefly due to the call battery or apparatus, which
must be carefully looked after if it is to work properly.
This drawback is more particularly experienced in large installations and
public telephonic networks, where every subscriber must be provided with a
separate apparatus, which is expensive to buy and to maintain in proper working
order.
All these drawbacks are obviated by the call system according to this invention,
in which there is only one generator for the whole of the subscribers.
According to this invention there are laid, beside the usual telephone wires,
other wires leading and branching off to each subscriber exactly like the telephone
wires and connected to the two poles of the central generator: Of course the
call wires must be carefully insulated from the telephone wires, to avoid
interruptions.
The call wires may be arranged either so that one wire leads from each pole of
the generator or the second pole is earthed. This second method, with earth
return, is cheaper as it necessitates the cost and laying of one wire only, and
besides it can be more easily insulated from the others.
Although laying two wires would be expensive, still even this would be much
cheaper than providing each subscriber with a separate generator or battery.
Therefore the call system for telephones connected in a network with a single
generator or battery consists in having at the central station a generator having
sufficient motive force to enable the current after it has arrived at the further-
most station of the net, to return back to the central station, but this time
through the separate line of the subscriber.
For this purpose, as has been mentioned before, a line or wire from one of the
poles of the common generator, of a cross section corresponding to the current
that has to go through it, is laid through the whole circuit of the net. The
other pole of the common generator connected to earth. The apparatus of
J

page_text: the subscriber is then shunted on to this circuit of the generator, one terminal of
the apparatus being connected to the wire from the generator and the other
terminal of the apparatus is connected to earth. The subscriber can then close at
will the circuit of the common generator. In order to make this arrangement
better understood it is represented by way of example in the accompanying draw-
ing in which an apparatus taken by way of example, as being the simplest to
represent in a drawing.
Each subscriber is provided with a special switch or contact device (shown in
Figures 2 and 3) connected to the central station and to the call generator.
Figure 1 illustrates the general arrangement of the system. The direction of the
current for effecting a call is as follows. Starting from the pole a of the
generator A it passes along the branch line to the switch B spring tongue 3
central plate d, line e to the central station; through the coil of the bell. or
indicator then along the line f central plate d', tongue 31 to line i to earth, thence
back to the negative pole of the battery.
As will be understood from the description of the switch device which will
be given hereafter, the above indicated effect is produced by pressing the button
of the switch.
Before the call is made and after being made, the upper tongues 3, 31 of the
switch are not in contact with the central plates d, d of the switch, while the
lower tongues 2, 21 i.e. those which communicate with the telephone apparatus C
of the subscriber, are in contact with the central plates and consequently, in a
position for speaking with the subscriber.
The circuit from the central station to the subscriber's telephone is as follows.
The current passes over the line f to the plate , tongue 21 line centering the
apparatus at and leaving at h, thence along the line j, tongue 2, plate d line e
back to the central station. This, of course, refers to the current coming from
the central station; the one from the subscriber's apparatus (for speaking only,
as I have already described how the calls are made) passes through the same
circuit only in the opposite direction.
But if all is arranged as described, that is to say, if the shunt circuit from
the circuit of the common generator is directly connected to the terminals of the
call-mechanism of the subscriber's apparatus, the result will be that, (as said
terminals are on a shunt circuit from the line wires connecting the apparatus to
the central station), when two or more subscribers who are on the same shunt
circuit from the generator talk, there will be a crossing of currents and con-
sequently each subscriber will over-hear the conversation of the others.
This difficulty is avoided by my new and simple switch which is inserted in
the line wires before they reach the apparatus. This switch is shown in plan in
Figure 2 of the accompanying drawings and in section in Figure 3.
The central plates d, d of the switch are connected to the wires of the separate
line of the subscriber, and are normally in contact with plates 2, 21 which are con-
nected to the apparatus. In this position of the switch the current from the
central station passes through the apparatus and operates the bell.
In order to call a subscriber, it is only necessary to press a button on the
plates 3, 31, whereupon by means of a small knob 4 of bone or rubber provided at
the end of the plates 3, said plates 3 force the plates 2, 21 to break contact
with the plates d, d, and connect the latter to the wires of the line of the
subscriber. As the plates 3, 31 are in communication, one with the pole of the common
generator and the other with the earth at the moment of their being connected to
the plates d, d, the circuit of the common generator is closed and there will
be generated in the line of the subscriber a current which will arrive at the
central station or at the apparatus of another subscriber with whom it is desired
to converse. When the knob is released the parts return to the positions they had
before the call was made.
If the call apparatus be worked by primary or secondary batteries, then the
arrangement must be as shown in the accompanying drawing. In case of a

page_text: dynamo being used for working the call apparatus, the dynamo must be con-
stantly running so that a subscriber may have current whenever required.
The dynamo may be driven either by a small turbine, gas-motor or the like, or
even by clock-work if it is desired to work economically.
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. In a telephone system the method of using a central generator for operating
the call-bells substantially as described.
2. In a telephone system of the kind described a switching device substantially
as described or illustrated in the accompanying drawings.
Dated this 13th dox of Tuna 1808
BOULT & WADE,
Agents for the Applicant.