Improvements in Telephonic Switching Apparatus.
Year: 1890

page_text: Date of Application, 29th Nov., 1890
Complete Specification Left, 20th Aug., 1891-Accepted, 17th Oct., 1891
PROVISIONAL SPECIFICATION.
Improvements in Telephonic Switching Apparatus.
ALFRED ROSLING BENNETT, 26, Booth Street, Manchester, Electrical Engineer,
do hereby declare the nature of this invention to be as follows:
The object of my invention is to improve and facilitate the working of telephonic
switch-rooms when the lines connecting the subscribers to such switch-rooms are
composed wholly or for the most part of metallic circuits.
The invention consists of an improved multiple switch-board.
The switch-board is divided into sections each section being of a size small
enough to be reached in every part by an operator and there are as many of these
sections as there are operators required to attend to the number of subscribers
connected to the switch-room. Each of the two wires of which a metallic
circuit is necessarily composed is continued from one end of the switch-board to
the other and has a suitable contact attached to it at intervals, these intervals
corresponding to the sections. Thus if ten operators are required to attend to
the subscribers connected to the switch-room there will be ten sections to the
board and each wire of each metallic circuit will have ten contacts attached
to it.
When a metallic circuit is out of use the contacts of the two wires composing
it are separated by a small insulating space or interval which may be simply air or
of some solid insulating substance like ebonite or india-rubber. In this condition
a current sent over the metallic circuit from the subscriber's office will have no
effect since it cannot pass the insulating space.
To bring a metallic circuit into use a plug or peg must be inserted into or
between the contacts. Such a plug must have two metallic parts separated from
each other by some insulating substance and so arranged that when inserted
one metallic part shall touch the contact attached to one wire of the metallic
circuit and the other metallic part shall touch the contact attached to the other
wire of the metallic circuit. If now the two metallic parts of the plug are con-
nected by means of conductors to the terminals of a telephone the metallic circuit
will be completed and brought into use.
When it is desired to connect any two of the metallic circuits on the switch-board
together two such plugs are employed, the metallic parts of one plug being joined
to the corresponding metallic parts of the second plug by means of conductors.
When such a pair of plugs is inserted into any of the contacts of any two of the
metallic circuits those circuits are telephonically joined together.
Since each metallic circuit has contacts at each section of the switch-board it
follows that any two circuits can be connected together at any section. The
contacts may be simply small blocks of metal attached by screwing, clamping or
soldering to the wires at the necessary intervals, the blocks having notches or holes
of shapes suitable for receiving the plugs. The insertion of a plug does not break
the continuity of any of the wires.
Dated this Twenty-seventh day of November 1890.

page_text: Improvements in Telephonic Switching Apparatus.
I, ALFRED ROSLING BENNETT, of 22, St. Alban's Road, Harlesden,
London, N.W., Electrical Engineer, late of Manchester, 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 invention relates to an improved multiple switch-board, that is to say, a
switch-board constructed so that each operator has the connecting contacts of every
subscriber within reach and is able to complete any connection that may be called
for without the aid of a second operator. The invention is applicable only
when the lines to be operated consist wholly or for the most part of metallic
circuits.
The switch-board is divided into sections as numerous as the number of sub-
scribers to be attended to requires. Each subscriber's line is represented on each
section by two contacts, one contact for each of the two wires of which a metallic
circuit is necessarily composed. The two contacts are placed close together so as
to be simultaneously touched by the insertion between them of a small contact peg,
or by the application of any other suitable form of circuit closer.
The two contacts are separated by a small insulating interval or space, which
may be simply an air gap or composed of ebonite or other efficient insulator.
The effect of this insulating space is to break the continuity of the metallic
circuit.
The leading feature of the invention is the connection of the metallic circuit to
these contacts in such a way that the insertion of a metal peg, or its equivalent,
between any pair of them shall close the circuit at that point. In technical
language the several pairs of contacts are in shunt or parallel arc in respect to the
two halves of the metallic circuit, and when the metallic circuit is represented by
contacts on several sections of the switch-board, the wires of which it is composed
may be compared to two electric light conductors having a number of electric
lamps strung between them, the contacts occupying the position of the lamps.
Supposing, for the purpose of illustration, contact pegs to be inserted in all the
contacts of the metallic circuit the invention will be given effect to by any method
of connecting the metallic circuit to the contacts which will cause a current sent
from the distant end of one of the wires of the metallic circuit to divide
between all the contacts and pegs in its passage to the other wire and back to
its source.
The metallic circuit has to be connected to its contacts on the several sections
either by direct extension to them of its two component wires, or by branches from
them. The simplest method of so connecting is shown at Figure 1 of the accom-
panying drawings, which represents a switch-board consisting of three sections,
together with the connections of three metallic circuits to their several contacts.
The metallic circuits are denoted by s, s; s¹, s; and s², s²; and the corresponding
contacts by sc, se; se², se¹; and sc², sc². The insulating spaces between the contacts
are indicated by the blank between each pair of semi-circles.
At Figure 3 is shown a method of connecting which is electrically identical
with the one just described. Instead of a metallic circuit, s, s, being continued
straight from contact to contact it is stopped short at the points P, P, and divided
into as many branches as there are sections, each branch being led separately to its
contacts, sc. For the sake of clearness the connecting wires of only one metallic
circuit are indicated in the figure.
At Figure 4 a third plan for connecting, electrically identical with the
two preceding ones, is shown, the metallic circuits and contacts being indicated
as before.

page_text: At Figure 5 is represented a fourth method of connecting so as to secure the
purpose of the invention. According to this method only one wire of each metallic
circuit is connected separately to its contacts. The other wires are stopped short
at a point, P, and having been joined all together are connected to the opposite
contacts by a common wire, v, v, v. The use of this method is attended
by drawbacks in practice since a fault, such as defective insulation, occurring
on one or more of the metallic circuits will injuriously affect all the others.
To bring a metallic circuit into use a contact peg, or a suitable equivalent, must
be inserted into or between its contacts on one or other of the sections of the
switch-board. Such a peg must have two conducting parts insulated from each
other and so arranged that when inserted one conducting part shall touch the
contact attached to one wire of the metallic circuit and the other conducting part
If now
shall touch the contact attached to the other wire of the metallic circuit.
the two conducting parts of the peg are attached by means of wires or conductors
to the terminals of a telephone or telegraphic instrument the metallic circuit will
be completed and ready for use. When it is desired to connect any two of the
metallic circuits on the switch-board together two such pegs are employed, the
conducting parts of one peg being joined to the corresponding parts of the second
peg by means of wires or conductors insulated from each other.
When such a
pair of pegs is inserted into the contacts of any two of the metallic circuits those
circuits are electrically joined together. It is characteristic of the invention that
the insertion of pegs does not break the electrical continuity of any of the wires.
Since each metallic circuit has contacts on each section of the switch-board it follows
that any two metallic circuits can be joined at any section.
Figure 2 represents in end and side section the general construction of such a peg
as is described, c, c, being the conducting parts, separated by an insulating
substance, i; and w, w, the connecting wires.
Figure 6 shows in end and side section a peg specially adapted for use when the
connections of the metallic circuits are made as in Figure 5.
The contacts provided for connecting purposes may be simply small blocks of
metal attached by screwing, soldering, or otherwise suitably, to the wires of the
metallic circuits at the intervals corresponding to the sections of the switch-board,
the blocks being provided with notches, holes, springs, sockets, or other suitable
devices for receiving and holding the pegs. The shape, size and details of the
contacts are not material, so long as they afford good electrical connection with the
pegs. It is, however, desirable that the contacts should be of small size in order
that space may be economised.
Having now set forth the general principles and characteristics of the invention,
I shall describe how it may be given effect to practically and adapted to the
purposes of a telephone exchange.
I take two flat, square plates of insulating material, as ebonite, measuring five
inches by five, and drill in each one hundred holes so that the centres of the holes
in each plate exactly coincide. Into each hole a metallic ferrule, ring, short piece
of tube, or socket, is inserted and fastened by means of small pins. The holes and
sockets should be smaller in one plate than in the other. The two plates are then
bolted together, the one with the smaller holes undermost, in such a manner that an
air space of about half an inch is left between the two plates and the centres of
the holes in one plate coincide exactly with those in the other. The arrangement
of plates with their fittings is clearly set forth in Figures 7, 8, 9 and 10 of the
accompanying drawings, in which, i, indicates the insulating plates; f, the sockets
and, b, the bolts holding the plates together. The metallic sockets are shown open
at both ends but those on the lower plate may be closed at the bottom without
detriment.
The sockets, f, constitute the contacts and are the equivalents of the parts, sc,
Figures 1, 3, 4 and 5.
in
A pair of sockets is reserved for each metallic circuit, one wire of such a circuit
being fastened to a socket on the upper plate and the other wire to the socket

page_text: 111
immediately below it on the lower plate. This arrangement is shown
Figure 9 where, c, indicates a cable containing one hundred metallic circuits,
5, 5; s¹, s¹ ; s², s²; three of them spread out and connected to their respective
and
sockets.
The details of a peg adapted for effectively connecting any two of the metallic
circuits together are shown in Figure 11. The peg consists of a metal pin, c,
enclosed in an insulating tube, i, which is in turn enclosed in a metal tube, c'. The
two metallic parts are kept from electrical contact by the intervening insulating
tube and are connected at their upper extremities to two insulated flexible
conductors made up into a cable or cord. The metal pin of the peg fits the
sockets on the lower plate while the metal tube fits the sockets of the upper plate,
this second connection being improved or rendered more certain by a supplementary
conducting piece, r, in Figure 11, which is attached to the metal tube by a short
metallic spring which is compressed when the peg is pushed home in the sockets.
By the compression of the spring the supplementary piece, r, is held firmly against
the top surface of the socket and compensates for any loose fitting between the
tube, e, and the socket. The fitting of a peg in the socket is shown in Figure 10
and a pair of inserted pegs with their connecting cord containing two insulated
conductors is shown in Figure 8 in the requisite position for joining telephonically
or electrically two of the metallic circuits.
The switch-board is made up of as many of these five-inch squares, each
containing contacts for one hundred metallic circuits, as may be required. The
squares are supported in a framework, shown in Figure 12, at m, m, m, m, which
may be fixed flat like a table, or vertically, or sloping.
A section of the switch-board may consist of any desired number of squares, but
five rows of ten squares each, accommodating five thousand metallic circuits, is as
many as an operator can conveniently reach over. The plan of a switch-board so
divided is shown in part in Figure 12, where the sequence of the connections to the
squares in the successive sections is indicated by the lines s to s³, representing the
course of one metallic circuit to each square. The squares of the sections are
indicated by 1 to 10; 1' to 10' and 12 to 10².
There is no provision on the switch-board for signalling, by means of electro-
magnetic indicators or equivalent devices, from the subscribers to the operators
as the invention is primarily designed for use with those switching systems,
such as the "Mann" system and the "Law "system, which dispense with such
accessories.
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. A telephonic switch-board adapted for metallic circuits in which the con-
necting contacts of each metallic circuit are separated by an insulating space when
out of use so as to break the continuity of the metallic circuit, substantially as
described.
2. The arrangement of the contacts of each metallic circuit at the different
sections of a multiple telephonic switch-board in shunt or parallel are, so that a
current arriving at the switch-board by one of the wires of a metallic circuit will
(in the event of contact pegs being inserted in all the contacts proper to that metallic
circuit) divide or split between all the said contacts and pegs on its way to the other
wire of the metallic circuit and so back to its source at the distant end of the
metallic circuit, substantially as described.
3. In multiple telephonic switch-boards adapted to metallic circuits the provision
of contact pegs arranged as and for the purposes described.
4. In multiple telephonic switch-boards the arrangement of contacts so that
the insertion of contact pegs does not break the continuity of any of the
connecting wires but, on the other haud, establishes continuity where it was before
non-existent.

page_text: 5. The methods of connecting the metallic circuits to the contacts sub-
stantially as described and shown in Figures 1, 3, 4 and 5 of the accompanying
drawings.
6. The mechanical arrangement, form and fitting together of the various parts
of the switch-board and contact pegs substantially as described and shown in
Figures 7, 8, 9, 10, 11 and 12 of the accompanying drawings.
Dated this Eighteenth day of August 1891.
A. R. BENNETT.