Improvements relating to Telephonic Switching Apparatus.
Year: 1892

page_text: Date of Application, 24th Aug., 1892-Accepted, 22nd Oct., 1892
COMPLETE SPECIFICATION.
Improvements relating to Telephonic Switching Apparatus.
I, ALFRED ROSLING BENNETT of 22 St. Albans Road, Harlesden in the
County of Middlesex, Electrician, 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 :-
My invention relates to telephonic switching apparatus and has for its object to
provide improved testing apparatus for use in a telephone exchange, whereby an
operator can, when called by any subscriber who wishes to be connected to another
subscriber, find out whether the said second subscriber is engaged.
My said invention is applicable to any system of exchange telephony wherein a
complete metallic circuit is used for the subscribers' lines.
In such telephone systems the connecting together of two subscribers' line wires
at the exchange is done by inserting the ends of flexible connecting cord
containing two insulated conductors in contact-blocks or sockets on the switch
board to which the subscribers' lines are attached.
In carrying my invention into practice I join one of the conductors of all of the
flexible connecting cords to a common lead or to earth, and provide as described
in my Specification of Letters Patent 12484 A.D. 1891 at every section of the
switch board in the exchange a metallic test tip or point which is joined electrically
by means of a flexible connection to any suitable indicating device such as a bell.or
telephone or the like, and I join all the said indicating devices to the common lead
above mentioned or to earth.
It is easily understood that any one of the flexible connecting cords has one of
its twin conductors joined and in electric connection with all of the testing tips or
points. I also provide a battery or other source of electricity which I insert at any
suitable point in the circuit above described, or a source of electricity may be
permanently inserted at any point in each subscriber's metallic circuit.
Instead of placing a source of electricity in the testing circuit I may arrange
that the circuit shall be acted on inductively by means of induction or phonoporic
coils or by means of condensers.
In order that my invention may be more clearly understood I will now proceed
to describe the same with reference to the accompanying drawings, in which
Figure 1 is a diagram illustrating part of a multiple switch-board provided with
the testing apparatus according to my invention.
Figure 2 is a similar diagram the contact blocks on the switch-board in this case
being arranged in series with the subscribers' line wires instead of in parallel
therewith.
Similar letters of reference denote corresponding parts in both the drawings.
In the drawings five subscribers' lines are shewn having connecting blocks on
three sections of the switch board. P₁ to P³ are the subscribers' telephones; M₁
to M³ the line wires; and S¹ S, S' denote three sections of the switch board.
Three flexible connecting cords are shewn having conductors C, C². T¹, T², T¹
are the test tips or points which are joined through indicating devices 11, 12, 13 by
wires T to a common lead E or to earth. One conductor C² of each of the flexible
connecting cords is joined by a wire B to a the common lead E or to earth. There
is therefore electrical connection between any one of the test tips or points T¹, T*,
T and any one of the flexible connecting cords C. In Figure 1 a battery or
other source of electricity V is shewn inserted in the common lead Ẹ but I may
obviously place the same anywhere in the testing circuit or 1 may join separate
batteries or sources of electricity in the wires T between the test tips and the
common lead or earthi as shewn in Figure 2 or place them in the wires. B.

page_text: Instead of placing the batteries or other sources of electricity in the testing
circuit at the exchange I may permanently insert a battery in each subscriber's
line wire.
In a modification of my invention I use an induction or phonoporic coil in
connection with the testing circuits instead of using testing batteries, for instance I
may insert the secondary of an induction coil in the common. lead. E and energize
the primary coil from a battery which is in a local circuit, I may also insert one or
more condensers at any point in the testing circuit, and in that case I provide an
intermittent or alternating source of electricity for the testing battery.
The operation of my improved testing device is as follows that is to say when
two subscribers are joined by a connecting cord in any section of the switch board
as shewn for instance in Figure 1 where P1, P2 are connected at S³ it is evident
that the line wires of both subscribers are in metallic connection with all the test
tips T, T2 in the exchange. Hence, if an operator at any section apply the test
tip or point to the connecting block of either of the said subscribers a current will
flow round the testing circuit thus giving a signal on the indicating device. If the
operator apply the test tip or point to the connecting block of a subscriber which
is disengaged no signal will be given by the indicating device. Hence when an
operator is called by a subscriber and asked to connect the same with a second
subscriber it can by the application of the test tip or point to any connecting
block on the second subscribers' line wire, be ascertained whether the said second
subscriber is engaged or not.
Having now particulary described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. In a telephone system with complete metallic circuits for the subscribers'
lines and multiple switch boards aud flexible connecting cords consisting of two
insulated conductors, the arrangement whereby one conductor of each of the said
connecting cords is electrically connected through a lead or through the earth with
all of the operators' testing tips, for the purpose specified.
2. In a telephone system with complete metallic circuits for the subscribers'
lines and multiple switch boards the combination with the same of a testing
apparatus substantially as described with reference to the accompanying drawings,
or the modifications thereof herein described, for the purpose specified.
Dated this 24th day of August 1892.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.