Improvements in Telephone Central Station Apparatus.
Year: 1888

page_text: Date of Application (in United Kingdom), 24th Sept., 1888
Complete Specification Left, 24th Sept., 1888
Complete Specification Accepted, 22nd Jan., 1889
COMPLETE SPECIFICATION.
Improvements in Telephone Central Station Apparatus.
We, THEODORE NEWTON VAIL, of 190 Walnut Street Boston, County of Suffolk,
State of Massachusetts, United States of America, Electrician, and JOHN ASHBY
SEELY, of 18 Cortlandt Street New York, County of New York, State of New York,
United States of America, Electrical Engineer, do hereby declare the nature of our
said invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :—
Our invention is an improvement in the arrangement of telephone apparatus,
whereby intercommunication between distant points is facilitated, while the space
occupied and the expense of erecting and maintaining such apparatus are reduced.
This improved apparatus is adapted for use in the multiple-board arrangement for
central stations, which is the most efficient system now known. The distinguishing
characteristics of this well known system are a series of duplicate boards, upon each
and every one of which the aggregate number of sub-station lines have electrical
connections. This aggregate number of lines or circuits is divided into a number of
groups, each group being substantially equal to the number of circuits which
experience has demonstrated that an operator can satisfactorily attend to. The
aggregate number of circuits divided by the number of circuits in a group gives the
number of separate boards, constituting the multiple board system, and upon each and
every one of which each and every wire has a spring-jack connection. Each circuit
of each group is furnished with a device for indicating or receiving calls, and a

page_text: suitable means for indicating the condition of every line is also auxiliary or incident
to every board and every circuit.
Experience has demonstrated that one central-station operator can under ordinary
circumstances care for about one hundred circuits. Such number, then, should
constitute the maximum in one group. If an exchange has an aggregate number of
five thousand subscribers, there will be fifty groups of one hundred each. There will
he fifty boards and five thousand spring-jacks on every board, or two hundred and
fifty thousand spring-jacks in all. We have then in the supposed multiple-board
central station five thousand subscribers' circuits, fifty boards, and fifty operators.
Each board has five thousand spring-jacks accessible to but one operator, one group
of one hundred circuits with their indicating devices, a telephone set, with testing,
calling, and looping in devices. This was the state of the art at or about the date of
our invention.
Our invention embraces the following improvements:
First One switch or circuit-changer being located in each of the aggregate
number of circuits, we assemble or focate such aggregate number of switches or
circuit-changes at one point, as upon a board—that is, locate them upon a frame or
table or in any equivalent manner, provided always that they be assembled within a
space accessible to or within reach of an operator without substantial change in his
or her position of support. We then take two or more groups or sub-divisions of this
aggregate number of circuits, each of which is provided with a special switch or
circuit-changer (such as a flexible conducting cord), designed to co-operate with any
switch of the aggregate number. These groups are separated from each other, but
are located in proximity to the aggregate number of switches. An operator is
assigned to each group, and from a position of support determined by the location
of the group the said operator has access to the aggregate number of circuits, as has
also the operator assigned to the second group and the third group, and so on.
Each
operator has charge of one group and is supplied with the necessary telephone set,
testing, calling, looping in devices, and clearing-out annunciators. The spring-jack is
the switch or circuit-closer used in the aggregate number of circuits, though we do
not limit ourselves to that specific form. The same is true of the jack-plug used as a
switching device for the circuits of each group. Thus in the supposed exchange of
five thousand circuits we place five thousand spring-jacks upon each board, which
board is so formed and arranged as to be accessible to a number of groups or to a
number of operators, each operator being supplied with necessary apparatus, and
the aggregate number of circuits is accessible to two or more, instead of being
accessible to only one group, or one operator, as has been the case in the best-known
arrangements. A very convenient arrangement is to place a board horizontally. We
prefer a board having the outline of a Greek cross. This presents eight available
positions for operators, each having before him or her the necessary indicating devices,
and other apparatus constituting a group, and to each one and all of which the
aggregate number of spring jacks, upon the surface of the board is accessible without
any substantial movement or change in the position of support of such operator.
Changes in the outline, of the board or table may, and probably will, suggest them-
selves coming within the principle of our invention, which further consists in so
arranging a board or a multiple-board system that the number of boards shall be only
equal in number to the quotient of the aggregate number of circuits divided by the
product of the number of circuits in a group into the number of operators-not less
than two-to which the aggregate number of jacks upon any one board is accessible;
or, in other words, divide the aggregate number of circuits by the product of the
number of circuits in a group into the number of groups at a table or board. In the
supposed exchange of five thousand subscribers, instead of employing fifty boards, we
should have at each multiple board eight operators and one hundred circuits for each
group. Dividing five thousand by eight hundred, we find that seven boards would
fill all requirements. Each board having five thousand jacks, we should have a total
of thirty-five thousand jacks in use in our improved system, as compared with two
hundred and fifty thousand jacks in the best arrangement heretofore known, and only

page_text: seven boards, occupying a limited space, as compared with my noards occupying
or seven times the floor-space. In our improved system there is also a great gain in
the matter of testing for lines in use, for every operator, when receiving a call can,
by simple inspection, immediately determine whether or not one seventh of the
aggregate number of lines are connected upon demand received over such line, while
in the present multiple board system, assuming the same number of circuitse,
one-fiftieth only can be determined by inspection, and the remainder must be
subjected to special test to determine the fact.
Second-We avoid the necessity for the use of special indicating devices to
receive calls or requests from sub-stations, and we only use an annunciator for
clearing out purposes, such clearing out annunciators being located upon a frame
fixed at a convenient angle to the position of the operator. Our improvement consists
in connecting every sub-station line of a group in multiple are with an operator's head
telephone and in terminating every sub-station line of a group in a flexible conducting-
cord normally resting by force of a gravity or equivalent take up upon strips,
conductors, or connections, forming the terminals of said operator's telephone. By
this means no preliminary signal is necessary, the sub-station merely removing his
telephone and speaking into the transmitter his own number or designation and the
number or designation of the sub-station required. The details and arrangement of
such a sub-station with certain novel and improved features we have described “in
another Application for Letters Patent bearing even date herewith No. 1377988.
Third We have also invented improved apparatus for calling in either direction
upon metallic circuit sub-station lines after they are united, in apparatus for looping
in an operator's telephone set after two sub-station circuits are united, and in the
arrangement or location of the clearing-out annunciators and the signaling and
indicating devices, all of which can be more satisfactorily described by reference to
the drawings.
Means for "testing" or determining whether or not any circuit of
the aggregate number not included in a group found on any particular table is in use
may be supplied, and may consist of one of the well known arrangements for that
purpose.
The accompanying drawings show our invention applied to metallic-circuit sub-station
lines.
Figure 1. shows the arrangement of the preferred form of board on which the
aggregate number of circuits each have a connection, the subdivisions or groups, and
the position of support of the operator assigned to each group. Fig. 1, is a detail
view of the arrangement of the annunciators.
Fig. 2. shows the details of a circuit having a connection upon each of three
boards, such circuit being assigned to a group at the last board.
Figs. 3, and, 3, are plan and sectional views, respectively, of the apparatus, forming
part of one group and of the connections forming a part of the aggregate number of
circuits immediately adjoining said group.
Fig. 4. illustrates the multiple board feature having our improvements applied
thereto.
There
In Fig. 1 there is a horizontally-fixed table or support having the outline of a
Greek cross.
The entire number of circuits entering the exchange have spring-jack
connections upon the face of this board, one hundred jacks being placed within each
square. (Indicated by dotted lines and by the figures marked on one wing of the
board.) We have denominated these the "aggregate number of circuits A.
are thus afforded eight positions of support for eight operators, g¹ to g, from each of
which an operator, without moving from such position of support, can reach any con-
nection or jack of the aggregate number. Each operator, as in the multiple-board
system, has a sub-division of the aggregate number under special charge, such
We prefer to assign
group being located in a position accessible to but one operator.
about one hundred circuits to each group and to terminate the circuits of a group in
flexible cords having a gravity take-up, w, as shown in Fig. 2.
We have shown and will describe our improvements as applied to circuits
having a "metallic return or "metallic circuits," as they are called, and we

page_text: will now. describe the connections of such a circuit and the apparatus assigned to each
group.
The circuit C Centers the first board G¹, passes through a spring-jack, j, forming
one of the aggregate number on that board, then through a similar jack on the second
board, G², then to the third board Ga³ and terminates, let us suppose, in group 9 on
that board in a flexible cord, m, having a double contact-plug, y, the two insulated
contacts at its base resting upon continuous strips or contacts 100 and 101, as shown
in Figs. 3 and 3ª where four such strips are shown in pairs. These strips or pairs
of strips form the group terminals of the opposite ends of say, one hundred
circuits, and also the terminals, respectively, of a local circuit, 90, 91, containing
a head-telephone, T, and a transmitter T, which are continuously in position for
use by the operator assigned to that particular group. It is to be observed, there-
fore, that the operator's head telephone and all the sub-station circuits of the group
are connected in parallel circuit, and any order or request telephonically transmitted
by a sub-station will be heard by the operator assigned to the group, who raises the
-plug p q and places it in the jack of the called-for circuit, which jack constitutes one
of the aggregate number on the same board, G³.
Each operator has push-buttons for ringing in either direction and keys for looping
a telephone into a circuit after it has been removed from its normal position. These
are shown in Figs. 2, and 3. c, indicates two separate push-buttons, a similar pair
being assigned to each circuit of a group. They consist of cylinders of insulating
material, each having two bands of conducting material, 9. and 11. 10. and 12.
15, 17, and 19 are three sections of conducting material, as are also 14, 16 18.
These sections form a continuous conductor, including the bands 9, 11, 10 and 12,
when the buttons are in a normal position. 1 and 2, 3 and 4 are bars of conducting
material, each forming the terminals of a generator of electricity. 5 and 7, 6 and 8
are contacts for uniting the line and generator when the buttons or either of them is
depressed. SS are springs for returning the buttons ce to their normal position.
The metal strip 21 furnishes a suitable bearing for the lower end of these buttons.
There is also a looping-in apparatus for each circuit. This is designed for use when
the plug is lifted from its normal contact and it is necessary or desirable to listen to
operations on the connected circuits. We provide electrical connections 40 41 from
the telephone set T to two fixed contacts 42 43, and the sub-station circuit is
electrically connected to two movable contacts, 44 45, as shown, so that by depressing.
button da telephone set is connected to the circuit independently of the normal
position of the apparatus and without disturbing the two circuits connected together
for conversation."
The two rows of plugs forming the terminals of one group are located in rows
before the operator of each group, as b₁ 68 Fig. 1. There are also two rows of
push buttons, as c² c³, and rows of looping-in keys, as dd. The clearing-out
annunciators are located upon frames a¹ to a³ at an angle with the position of the group
apparatus and immediately adjoining it. These annunciators, however, are only
intended, to be used for "ringing off."
The capacity of the board, as illustrated, is an aggregate number of five thousand
jacks and eight groups, the aggregate number being accessible to any one of the
eight operators without substantial change in the position of support-that is, no
spring-jack is out of reach of any operator. If an exchange have a greater number
than that assumed and the aggregate number of jacks cannot be more compactly
arranged, other arragements may be resorted to to obtain more space within reach of
a fixed position. To afford more space for the groups and accompanying operators,
the tables are duplicated as in the multiple-board system, which we have illustrated
in Fig. 4.
There is here shown a series of circuits, each and all of which have a connection
forming one of the aggregate number A on each and every board G G G³. These
circuits are divided into groups terminating in one of the eight groups assigned to
cach board, as g' or go, the number of boards required being equal to the aggregate
number of circuits (five thousand) divided by the product of the number of circuits

page_text: in a group (one hundred) into the number of groups at a table (eight)-that is, five
thousand divided by eight hundred is equal to seven-the smallest whole number
which will accommodate all the circuits and groups.
We will now describe the operation of receiving a call and connecting two sub-
stations, referring to Figs. 1, and 2. We have a connection with every circuit before
us in the aggregate number A. Our operator has the head telephone in position.
This telephone is normally connected with one hundred circuits, forming a group g²,
let us suppose.
A call is heard, "200 on 900," the first being the number of the
calling station, the second that of the station called for. The operator immediately
raises plug pg of the circuit 200, and if circuit 900 is idle places said plug in spring-
jack 900. This breaks circuit 900 at points in its jack, and the points p and
of the two contact-plugs connects with points and y, respectively. (See Fig. 2, G³.)
The two metallic circuits now form one continuous metallic circuit containing a
clearing out annunciator at the central station only, being free from the central station
telephone because all behind the jack j of circuit 900 is cut off and the plug of
circuit 200 is lifted from its telephone-contact. The central station now depresses the
rear push-button to signal the called-for sub-station, circuit passing from circuit 900
to plug pg, thence via elements 18, 12, 8, 4, B¹, 3, 6, and 19. The called-for station
responds and the conversation is carried on, as is well understood.
Should the central-station operator desire to listen, key, d, is depressed, connecting, 42,
with, 45, and, 43, with, 44, circuit being from the transmitting station to plug, P, 4,
thence mia cord, m, to point, 45, 42, 40, T, T', 41, 43, and, 44, to cord, m. When
conversation is concluded the calling-station sends an impulse from a generator to
line, dropping the annunciator, and the parts are then restored to their normal position
by the operator.
We have shown a spring-jack having a dust-guard, p', and a jack-plug, p, q, having
two or more contacts in a position to register with two or more fixed contacts, and
means whereby the said plug when retracted by the gravity take-up will always
assume the same position; but these features of improvement we have described and
claimed in the specification of another application, filed by as in the United States
Patent Office. March 1. 1888. Serial No. 265783. and for which we shall duly
make Application for British Letters Patent under the International and Colonial
Arrangements.
We do not herein claim the multiple arc arrangement of line-wires with a
telephone in a local circuit at the central station, as that also forms the subject-
matter of another application filed by us in the United States Patent Office.
April 20. 1888. Serial No. 271296. and for which also we shall duly make Application
for British Letters Patent under the International and Colonial Arrangements.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
:-
1. The combination of an aggregate number of series of electrical circuits connecting
a central station with a series of sub-stations, a telephone-instrument at each sub-
station, at the central station a series of spring-jacks or circuit-changers-one for
each circuit-located in close proximity on one board, two or more groups or sub-
divisions of said circuits separated from each other, located at said board, each having
a second switch or circuit-changer co-operating with the switches or circuit-changers
of the first-named series and located in close proximity thereto, whereby any circuit
of the first-named series and any circuit of either subdivision may be connected
together, substantially as hereinbefore described.
2. The combination of an aggregate number or series of electrical circuits connecting
a central station with a series of sub-stations, telephonic instruments at each sub-
station, at the central station a series of switches or circuit-changers, one for each
circuit, two or more separated groups or subdivisions of said circuits, each having a
switch or circuit changer co-operating with the switches or circuit-changers of the
first-named series, but located on the same board in proximity thereto, whereby any

page_text: circuit of the first-named series and any circuit of either subdivision may be
connected together, and a receiving-telephone common to the circuits of each group
or subdivision to receive calls or communications therefrom, substantially as. herein-
before described.
3. The combination of an aggregate number or series of electrical circuits connecting
a central station with a series of sub-stations, a telephonic instrument at each sub-
station, at the central station a series of spring-jacks or circuit-changers, one for each
circuit, fixed in close proximity, two or more groups or subdivisions of said circuits
separated from each other, but at the same board, each circuit of a group terminating
in a flexible conducting-cord, and a jack-plug co-operating with the spring jacks of the
first-named series and normally resting in close proximity thereto, whereby any
circuit of the first-named series may be connected with any circuit of either group or
subdivision, substantially as herein before described.
4. At a telephone station, a switch-board having the form or outline of a Greek
cross, an aggregate number of electrical circuits, each circuit uniting a central
station and one sub-station, a series of electrical connections-one for each circuit―
located on said switch-board, means for connecting circuits in pairs, eight sub-
divisions or groups of said circuits, eight electro-magnetic receiving-instruments, one
for each group, each instrument being common to all circuits of its group, and eight
positions of support for eight operators, one for each group, said positions being so
located that one group and the aggregate number of circuits are accessible to an
operator therefrom, substantially as hereinbefore described and shown in Fig. 1.
5. The combination of two or more switch-boards each having the form or outline
of a Greek cross, duplicate electrical connections with an aggregate number of
circuits on said boards, means at each board for electrically connecting circuits
together, eight different subdivisions or groups of said circuits at each board, and
separate indicating devices for each group, the whole being so arranged that eight
operators may be assigned to each board, one operator to a group, cach operator
being in a position of support accessible to one group and to one and the same series
of connections with the aggregate number of circuits, substantially as hereinbefore
described and shown in Figs. 1 and 4.
6. The combination of an aggregate number or series of electrical circuits connecting
a central station with a series of sub-stations, a telephonic instrument at each sub-
station, at the central station a series of duplicate switches or circuit-changers in
each circuit of the aggregate number, one switch for each circuit, being located upon
each of a series of boards or frames in close proximity, two or more groups or sub-
divisions of said circuits located upon each board or frame, each circuit of each
group having a second switch or circuit-changer, said groups being separated from
each other, but located in close proximity to the switches connected with the
aggregate number of circuits, the number of boards or supports being equal to the
aggregate number of circuits divided by the product of the number of groups at a
board into the number of circuits in a group, substantially as hereinbefore described.
7. The combination of an aggregate number or series of electrical circuits connecting
a central station with a series of sub-stations, a telephonic instrument at each sub-
station, at the central station a series of spring-jacks or circuit-changers, one for each
circuit, fixed in close proximity, two or more groups or subdivisions of said circuits
separated from each other, but at the same board, each circuit of a group terminating
in a flexible conducting-cord, and a jack-plug to co-operate with the spring-jacks of
the first-named series and normally resting in close proximity thereto, a receiving-
telephone common to each circuit of a group, and a ringing-off annunciator in each
circuit, substantially as hereinbefore described.
8. At a telephone-station, the combination of a metallic circuit consisting of two
substantially parallel wires or conductors united at or near their terminals, a switch
or circuit-changer located in said circuit intermediate said terminals, two pairs of
fixed contacts and one pair of movable contacts equally divided between and normally
forming part of the circuit of both wires, a third pair of fixed contacts and a second
pair of movable contacts, a generator of electricity having its opposite poles connected

page_text: to one pair of said contacts, and a base of insulating material upon which the two
pairs of movable contacts are located, all said contacts being so located with respect to
each other that a predetermined change in position of said insulating-base.removes a
fragment of the circuit and substitutes said generator therefor, substantially as herein-
before described.
9. At a telephone-station, the combination of a metallic circuit consisting of two
substantially parallel wires or conductors united at or near their terminals, two
switches or circuit-changers located in said circuit intermediate said terminals, each
switch consisting of two pairs of fixed contacts, one pair of movable contacts equally
divided between and normally forming part of the circuit of both wires, a third pair
of fixed contacts and a second pair of movable contacts, a generator of electricity
having its opposite poles connected to one pair of contacts of each switch, and a base
of insulating material for each switch, upon which the two pairs of movable contacts
are located, the contacts composing the two switches occupying reversed positions,
respectively, and the contacts of each switch being so located with respect to each
other that a predetermined change in position of one of said insulating-bases divides
the line and substitutes the generator for one half a section thereof, while a similar
change in position of the second insulating-base divides the line and substitutes the
generator for the other half or section, substantially as hereinbefore described.
Dated this 4th day of September 1888.
THEODORE NEWTON VAIL.
JOHN ASHBY SEELY.