IMPROVEMENTS IN THE ARRANGEMENT OF CIRCUITS AND APPARATUS. TO BE USED IN CONNECTION WITH TELEPHONIC COMMUNICATION
Year: 1883

page_text: LETTERS PATENT to Sydney Pitt of Sutton in the County of Surrey for an
Invention of "IMPROVEMENTS IN THE ARRANGEMENT OF CIRCUITS AND
APPARATUS. TO BE USED IN CONNECTION WITH TELEPHONIC COMMUNICATION
communicated to him from abroad by Charles E. Scribner of Chicago United
"
States of America
"
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office
of the Commissioners of Patents on the 22nd June 1883.
ر
334
SYDNEY PITT of Sutton in the County of Surrey 'IMPROVEMENTS IN THE
ARRANGEMENT OF CIRCUITS AND APPARATUS TO BE USED IN CONNECTION WITH
TELEPHONIC COMMUNICATION [communicated to him from abroad by Charles
E. Scribner of Chicago United States of America]
This Invention is an improvement upon the system of telephonic exchange.
described in Letters Patent dated the 29th November 1879 Number 4903
The Invention herein described is designed to be used on what is known as the
Central Office system and consists.
(1) In the testing apparatus for multiple switch boards.
The individual telephone lines are connected each with a single switch or spring
jack on each of the multiplo boards. The spring jack which it is preferred to use,
consists of an insulated spring which ordinarily rests in contact with the insulated
contact point the spring and point being mounted on a frame. The frames of the
switches of a given telephone line are all connected together by means of a suitable
wire connection.
The spring jack switches of a given telephone line may be considered as a series
of switches distributed on different boards; and the frames of the different series
are connected together by means of the wire connection above mentioned.
Ordinarily the frames of the switches of a given series remain insulated from the
line of said series when a plug is inserted in any one of the spring jack switches
of the series, the spring heretofore described is disconnected from the insulated
contact point and the frame and spring of the switch are connected with the
metallic portion of the plug. It will thus be seen that as the frames of a given

page_text: series are connected together, when any given frame is connected with a plug all
the other frames of said series will be connected with the same plug. The line
which connects the frames of the different switches of a series, however, being
normally open it is evident that when this connecting line is connected to the
subscribers telephone line at only one point it will still remain open, therefore
after a connection is made at any given switch of a line the circuit of said open
test circuit may be closed at any other of the switches, and the invention consists
in the use of testing apparatus with the system of circuits heretofore described.
The testing apparatus which it is preferred to use consists in a battery and bell or
relay provided at each multiple board and a connecting piece adapted to be applied
to the frame of any of the spring jacks upon said Board. Let us suppose that
one Subscriber has asked to be connected with another Subscriber, by appling
this connecting piece to the frame of the spring jack of the subscriber wanted a
If his line is not in use
test may be made to determine whether his line is in use.
the battery will remain open and no signal will be given. If however the line of
the Subscriber wanted is connected at any other of the boards the battery will be
closed to line, and the bell telephone or other signal device will indicate that
the line is in use, and the calling subscriber will be notified thereof and instructed
to wait.
(2) The invention consists in an automatic system of circuits for connecting
the spring jack switches of two Subscribers together.
This apparatus may be applied to multiple systems or to systems in which
only a single switch board is used; and consists in the connecting piece with
which the different pairs of plugs are normally in electric contact. Horetofore it
has been necessary in order to bring the operators telephone into the circuit of a
subscribers line to press upon a key designed specially for this purpose
By the use of the present invention this extra work of the operator is dispensed
with, and connection is made between the subscriber who sends in the call and
the operator as soon as one of the plugs of a pair is inserted in the spring jack of
the calling subscriber since the circuits are so arranged that the other plug of the
pair rests in contact with the cominon connecting piece, and this common connecting
piece is connected through the operators telephone to ground-Upon lifting the
second plug of a pair the listening operators Telephone is automatically disconnected
from both the conducting cords of the pair
(3) The invention consists in the system of circuits for the subscribers of the
Telephone lines
Each line is connected from the subscribers station to the spring of the spring
jack upon the switch board and thence through an annunciator, and thence to a
common line which extends back to the subscribers station. This common line is
connected to the ground at the central Office-In multiple switch board systems
the line extends from the subscribers station to the spring of the switch upon the
first of the multiple boards, and thence the circuit may be traced through said
spring and the contact point of the switch to the spring of the switch of the line
upon the second board, and thence through the contact point of the switch upon
the second board to the third board and so on to the last board, and thence through
the annunciator of the line; after passing through the annunciator the circuit is
the same as heretofore described extending back to the subscribers office by a line
connecting with a common line
This common line is provided with a ground connection. By this arrangement
of circuits all the advantages of metallic circuits for the neutralization of induced
currents are obtained without the disadvantages of complicated switching
apparatus heretofore employed for connecting together metallic circuits
The ordinary switching apparatus employed with single wires being readily
adapted to this particular system of circuits
(4) The invention consists in a Telephone made light so that it may be worn at
the ear of a listening operator without fatigue
A thin soft iron case extends from the rear pole of the Electro-magnet of the

page_text: Telephone to the soft iron diaphragm there of said pole is thus extended to the
central portion of the diaphragm. No permanent magnet is used. The coils of the
Electro magnet of the Telephone are connected through a battery and one of the
windings of an induction coil, the other winding of the induction coil is included
in the circuit of the Telephone line. Telephonos constructed in this manner
weighing only two ounces work successfully
A modified form of the testing apparatus consists of a polarized annunciator
and battery included in the circuit of each pair of connecting cords, which is
especially adapted to multiple switch board systems
The circuits of the Telephone lines may be run from the subscribers station to
the central Office in the usual manner. The ordinary spring jack switch may be
employed which consists of a metallic tube, which serves as a metallic frame upon
which is mounted a spring, which normally rests upon an insulated contact point.
The circuit of a Telephone line may be traced to the frame of a switch upon the
first board, and thence to the switch of the line upon the second board, and thenco
to the third board, and from the contact point upon the last board through an
annunciator to ground A bell or other signal device is also provided in a normally
open ground circuit at each of the boards. By means of a suitable connecting
piece which is adopted to be applied to the frame of the switches a test may be
made to determine whether the line of the subscriber called for is in use-For
example if a lino wanted at the first board were connected at the second board
by the pair of cords heretofore described, the operator at the first board could
determine the fact by applying the connecting piece to the switch upon the first
board of the line of the subscriber wanted. The connecting piece when thus
applied to the switch would tap the circuit of the battery included in the pair of
cords at the second board and this circuit would be sent through the bell or other
signalling device at the first board thus notifying the operator at the first board
that the line asked for is in use
Another modification of the testing apparatus consists in the use of a condenser
with the ordinary annunciator in the circuit of each pair of connecting cords; and
testing apparatus at each of the multiple switch boards the testing apparatus
consists of a loop including a battery, signalling apparatus and a double or loop
plug. If a line wanted at the first board is in use at: the second board the fact
may be determined at the first board by inserting the loop plug in the switch of
the said line.
i.
Since the condenser is included in the circuit of the connecting cords at the
second board, the battery of the signalling apparatus at the first board will be
open at the condenser. If the line be not in use at any of the other boards the
circuit, of the battery will be closed from the ground at the Central Office to
the ground at the Subscribers Station and the bell of the signal apparatus
ringing will notify the operator at the first board that the line is disengaged and
the Operator will thereupon proceed to make the usual connection

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Sydney Pitt in the Great Seal Patent Office on the
21st December 1883.
SYDNEY PITT of Sutton in the County of Surrey "IMPROVEMENTS IN THE
ARRANGEMENT OF CIRCUITS AND APPARATUS TO BE USED IN CONNECTION WITH
"
TELEPHONIC COMMUNICATION A communication to me from abroad by Charles
E. Scribner of Chicago United States of America
The invention herein described is designed to be used as what is known as the
Central Office system.
I
The invention consists in the testing apparatus for multiple switch boards. The
individual telephone lines are connected with a single switch or spring jack on
each of the multiple boards. The spring jack which it is preferred to use consists
of an insulated spring which ordinarily rests in contact with the insulated contact
point the spring and point being mounted on a frame. The frames of the switches
of a given telephone line are all connected together by means of a suitable wire
connection. The spring jack switches of a given telephone line may be considered
as a series of switches distributed on different boards and the frames of each of the
different series are connected together by means of the wire connection above
mentioned. Ordinarily the frames of switches of a given series remain insulated
from the line of said series. When a plug is inserted in any one of the spring
jack switches of a series the spring heretofore described is-disconnected from the
insulated contact point and the frame and spring of the switch are connected with
the metallic portion of [the plug. It will thus be seen that since the frames of a
given series are connected together when any given frame is connected with a plug
all the other frames of said series will be connected with the same plug. The line
which connects the frames of the different switches of a series however being
normally open it is evident that when this line is connected to the subscribers
telephone line at only one point it will still remain open: therefore after a
connection is made at any given switch of a line the circuit of said open test
circuit may be closed at any other of the switches and the invention consists in
the use of testing apparatus with the system of circuits heretofore described.
The testing apparatus which it is preferred to uso consists of a battery and bell,
relay or telephone, provided at each multiple board and a connecting piece adapted
to be applied to: the frame of any of the spring jacks upon said board. Let us
suppose that one subscribor has asked to be connected with another subscribed.
By applying this connecting piece to the frame of the spring jack of the subscriber
wanted a test may be made to determine whether his line is in use. If his lino
is not in use the battery will remain open and no signal will be given. If however
the line of the subscriber wanted is connected at any other of the boards the
battery will be closed to line and the bell or other signal device will indicate that
the line is in use and the calling subscriber will be notified thereof and instructed
to wait.
This portion of the invention is shown in Figure 1 of the Drawing in which
three multiple switch boards 1. 2. 3 are shown in section.
Two subscribers stations A and B are shown. The subscriber's outfit may
consist of the usual bell telephone, transmitter, generator, induction coil, local
battery and switch. The individual line C of subscriber A extends to the
insulated spring of switch D upon board 1 and thence by insulated contact E and
line F to the spring of switch G upon board 2 and thence in, the same manner

page_text: On lifting one of the plugs of a pair as S and inserting it in the spring jack of
a line the circuit of the line will be directed to the plug so inserted and thence
may be traced to the other plug S¹ and by metallic portion S₁ to the connecting
strip T and thence to ground through the telephone T.
The line of a subscriber who has sent in a call is thus connected through the
operator's telephone automatically as a plug of a pair is inserted in his switch. The
operator listening at the telephone is told by the subscriber what other subscriber
he wishes to talk with and the operator thereupon inserts the other plug of the
pair of plugs in the switch of the subscriber wanted. As soon as this last plug is
lifted from the common connecting strip T the operator's telephone will be discon-
nected automatically from the subscribers line. The subscriber called for may be
notified by depressing the calling key and throwing current to his line in the usual
manner.
The telephone key T is included in a branch circuit preferably connected to the
circuit of the pair of plugs between the two spools of the coils of the electro-magnet
of the clearing out annunciator. It is evident that by depressing key T the
circuit of the two connected lines may be tapped through the telephone and the
operator by thus tapping the circuit may listen out in case the subscriber omits to
send in the clearing out signal.
The invention as thus described is adapted to systems of telephone exchango
where only one switch board is used. The system of connecting the spring jack
switches of the different lines is however equally adapted to multiple switch board
systems.
It is preferred to provide weights to hold the slack of the cords drawn out of
the way below the table or leaf of the switch board. The weights also serve to
hold the metallic portions of the plugs in contact with the common connecting
piece as shown in Figure 1.
Bubscribers stations.
At each subscribers station is provided the usual outfit consisting of a telephono
transmitter, induction coil, battery, switch, generator and bell.
At the central office is provided a switch board and the usual operators apparatus
which consists of the individual annunciators in the different lines, the telephone,
clearing out annunciators and switching apparatus.
The subscribers lines after passing through the central office are connected with
a common line which extends back to the subscribers station. This common line
is connected to the ground at the central office.
By this arrangement of circuits all the advantages of metallic circuits for the
neutralization of induced currents are obtained without the disadvantages of com-
plicated switching apparatus heretofore employed for connecting together metallic
circuits. The ordinary switching apparatus employed with single wires being
readily adapted to this particular system of circuits.
The invention is illustrated in Figures 1 and 3 of the Drawings.
In Figure 1 the stations A and B are shown connected as heretofore described
with the switches upon the multiple switch boards 1. 2 and 3 and through the
individual annunciators.
Any other form of spring jack switch may be used upon the switch boards as
for example the jack knife switch of Patent N° 4903 of November 29th 1879 or the
'forin shown in Figure 4 of the Drawing.
After passing through the annunciators the lines aro bunched together and con-
nected to a common connecting piece. This common connecting piece is indicated
by the wire U. A plate or other metallic piece may be used instead of the wire.
This common wire U serves as a ground connection for all the wires and should be
of high conductivity. The wires may however be run to ground separately.

page_text: suitable connecting piece which is adapted to be applied to the frame of the switches
a test may be made to determine whether the line of the subscriber called for is in
use. For example, if a line wanted at the first board were connected at the second
board by the pair of cords heretofore described the operator at the first board
could determine the fact by applying the connecting piece to the switch upon the
first board of the line of the subscriber wanted. The connecting piece when thus
applied to the switch would tap the circuit of the battery included in the pair of
cords at the second board and thus the circuit would be sent through the bell or
other signalling device at the first board thus notifying the operator at the first
board that the line asked for is in use.
This is illustrated in Figure 4 of the Drawing. Two telephone lines a and b aro
shown connected with switches upon three multiple boards in the usual manner.
At each board an open ground circuit with a connecting piece c is provided which
is adapted to be connected to any switch of the switch board to which it belongs.
In the circuit of each pair of connecting cords I provide a battery d and polarized
clearing out annunciator e. The polarized annunciator is shown in detail in
Figure 5.
The operator's telephone and calling apparatus are not shown in the drawing.
They may be arranged in the usual way and aro too well known to require
description.
An operator at one board before connecting the line called for with that of the
calling subscriber makes a preliminary test to determine whether the line is in use.
He does this by connecting the open earth circuit which contains the electro-
magnet of a bell or other instrument with the line of the subscriber called for.
This is shown at the first board the contact piece c being held against the frame
of the switch of line b. As the line is alrondy in use at the second board the
circuit of the two connected lines will be tapped when the piece c is applied to the
frame of the switch. Current will thus be directed from the battery d which is
in circuit at the second board through the electro magnot of the signal instrument f
at the board where the test is made. The operator at the first board will thus be
notified that the line is in use and inform the subscriber who sent in the call. If
the operator gets no response from his signal instrument he will know that the
line is not in use and will then make the desired connection.
Since a line in use at one board is cut off from all succeeding boards it follows
that it is unnecessary to make the test at the last board since if a line is in use it
will be found open when the operator attempts to send current to line.
VI
Another modification of the testing apparatus consists in the use of a condenser
with the ordinary annunciator in the circuit of each pair of connecting cords and
testing apparatus at each of the multiple switch boards
The testing apparatus consists of a loop including a battery signalling apparatus
and a double or loop plug. If a line wanted at the first board is in use at the
second board the fact may be determined at the first board by inserting the loop
.plug in the switch of the said line; since the condenser is included in the circuit
of the connecting cords at the second board, the battery of the signalling apparatus
at the first board will be open. If the line be not in use at any of the other
boards the circuit of the battery will be closed from the ground at the central
office to the ground at the subscribers' station and the ball of the signalling
apparatus ringing will notify the operator at the first board that the line is
disengaged and the operator will thereupon proceed to make the usual connection.
In Figure 6 of the Drawing I have shown a diagram of this testing system.
Figure 7 is a detail of the connecting plug, the shank except the point being
insulated by a rubber sleeve. Figure 8 is a detailed view of the double pointed or
loop plug used for testing
¿.
By inserting this loop plug in the switch of a line wanted the battery 9 and

page_text: bell will be looped into the circuit of the line as shown at the first board of
Figure 6. If the line is in use at any other board for example as shown at the
second board the circuit of the line will be opened by the condenser i to the
battery g and the bell will not ring.
If however the line is not in use the circuit will be closed to the battery g and
the bell h ringing will be a signal that the line is not in use and the operator will
proceed to make the usual connection.
It should be noted that the points k of the spring jacks are not insulated from
the frames. The electro-magnet of bell h should be of sufficient resistance to keep
the individual annunciator from being thrown down when a test is made.
As lines in use are cut off from succeeding boards it is not necessary to make a
preliminary test of the last board to determine whether a line called for is in use.
If the line is in use the fact will appear when it is attempted to throw current to
line to call the subscriber wanted.
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
First A normally open line N in combination with each series of switches and
testing apparatus at each board substantially as specified.
Second In a telephone exchange the combination with the different series of
switches of an open circuit provided with a contact piece near each switch of the
series and individual telephone line or lines connected with each of the switches of
the series to which it belongs.
Third-The line N connecting the insulated pieces M M M³ of the switches of
a telephone line C whereby an operator at one board may make a test to determine
whether the line when called for at his board is connected at any other of the
multiple boards.
Fourth A normally open earth circuit including a battery and the electro-
magnet of a signalling instrument at each of the multiple boards in combination
with the switches of the different boards and the lines connecting the insulated
portions of the switches of the different series together substantially as and for the
purpose specified.
Fifth The common connecting piece with which the plugs are normally in
contact and circuits as described whereby the telephone line with which one of a
pair of plugs is connected may find circuit through the operator's tolephone, said
telephone being disconnected automatically therefrom when the other plug of the
pair is lifted substantially as and for the purpose specified.
Sixth The combination with the switch board of a telephone exchange of a
pair of plugs and flexible cords one of said plugs being adapted to be inserted in
a switch upon the switch board while the metallic portion of the other plug
remains in contact with the common connecting piece of the operator's telephone
whereby the circuit is closed through said telephone substantially us and for the
purpose set forth.
Seventh-The combination of pairs of plugs each provided with a metallic
portion, said portions being adapted to be held in contact with a common
connecting piece by means of weights conducting cords and the telephone switches
upon the switch board whereby when one of a pair of plugs is inserted in a switch
the line of said switch will be connected through the operator's telephone, said
telephone being disconnected automatically when the other plug of said pair is
raised to be inserted in a second switch.
Eighth The combination in a telephone exchange system of metallic circuits
grounded at the central office substantially as and for the purpose specified.
Ninth The combination of several metallic telephone circuits in a cable
connecting the subscribers of the different stations with their switches upon the
switch boards and the annunciators and a ground connection substantially as and
for the purpose specified.
Tenth The telephone switch shown in Figure 1 the frame of which is

page_text: insulated from the spring and contact point substantially as and for the purpose
specified.
Eleventh The operators telephone consisting of the electro-magnet in combi-
nation with the light soft iron case attached to the rear of the core and the
diaphragm placed upon the front of the case whereby the poles of the electro-
magnet are brought near each other and the weight of the telephone reduced as
and for the purpose specified.
Twelfth The combination with multiple switch boards of pairs of conducting
cords each pair including a polarised annunciator and battery and a normally open
earth circuit at different boards whereby current may be directed through a signal
instrument from the battery in the pair.of cords connecting two lines substantially
as specified.
Thirteenth The combination in a multiple system of switch boards of pairs of
conducting cords and condensers a condenser being in the circuit of each pair of
cords and testing apparatus at the different boards substantially as specified.
Fourteenth-A switch provided with a frame and spring said spring being
insulated from the frame a contact point or lug upon said frame upon which said
spring normally rests and a connecting plug provided with insulating material
said plug being adapted to be inserted in said switch whereby said spring is lifted
from said lug or contact point and connected to the point of the plug substantially
as and for the purpose specified.
Fifteenth. The combination with two connected telephone lines with a condenser
in circuit at the central office of a testing circuit containing a battery and
signalling device adapted to be looped into the circuit of the connected telephone
lines substantially as and for the purpose specified.
-
--
In witness whereof I the said Sydney Pitt have hereunto set my hand and
seal this fifteenth day of December in the year of our Lord One thousand eight
hundred and eighty three.