Improvements in Telephonic 'Apparatus.
Year: 1890

page_text: [The decision of the Comptroller-General, of the 13th day of June 1893, allowed,.
under Section 18 of the Patents, &c. Act, 1883, an Amendment of this
Specification.]
Date of Application, 12th June,, 1890-Accepted, 19th July, 1890
COMPLETE SPECIFICATION (AMENDED).
Improvements in Telephonic 'Apparatus.
I, JOHN EDWARD KINGSBURY of 79 Coleman Street, in the City of London,
Manager, (a communication to me from abroad by the Western Electric Company of
Chicago, Illinois, United States of America) 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 :-
This Invention relates to that class of multiple switch board circuits in which
metallic telephone lines and single circuit or grounded lines are connected with the
same exchange.
"It applies especially in the use case where the operator's apparatus and circuits are so
arranged as to avoid the effects of induced currents from other circuits in connection
with a uniform test för all the lines.
1.
.
When two lines are looped together in metallic circuit the opposite sides of the
metallic circuit thus formed are connected to ground, on one side through a self
induction coil and on the other side through a self induction coil and test battery.
In the references to this portion of my invention in the first claiming clause hereof the self
induction coil is referred to as a retardation coil both expressions meaning a coil of wire
wound round a magnetic core and introduced for the purpose of blocking telephonic vibra-
tions. In the said case, however, I the Western Electric Company formerly have found
it necessary, to provide a special plug for making the test since the regular connecting
plug of each pair could not be used for testing in case a metallic circuit subscriber
called for a single circuit subscriber, as in such case there would be a false signal,.
resulting from the circuits connected with the test battery.
£
My Invention herein as referred to in the 2nd 3rd and 4th claiming clauses is designed
to avoid the necessity of using a special test plug; this I accomplish by means of a.
condenser placed in the circuit of the operator's telephone set and a proper switching
device.
The loop switch which I preferably employ is of special construction and the circuits.
connected therewith are so arranged in connection with the 'condenser that' one loop
plug of a pair may be used for answering any subscriber's call while the other loop
plug of the pair may be used is testing the line called for and in making the
connection therewith. The loop plug of a pair which is connected with the calling
subscriber's line is sometimes spoken of as the answering plug, while the other plug..
that is the one used to connect with the called subscriber's line, is sometimes termed
the connecting plug. It is the connecting plug that. I use in testing the "line
called for.
1
id
When the operator's telephone set is switched into circuit of any pair of cords by
means of the cam lever, the condenser, is brought in the strand connecting the tips
of the cords, that is to say, in the strand which connects together the terminals of the
two plugs which are designed to be connected with the springs respectively of: the-
spring jack switches of any two lines with which they are connected. When:

page_text: the answering plug is inserted to connect with any calling subscriber's line, a circuit
is formed from the test battery to the sleeve of said plug and thence connection is
made with the several test pieces of the line, and thence the circuit may be traced
over the limb of the metallic circuit connecting with said test pieces to the sub-
scriber's station and thence back over the other limb of the metallic circuit to the
spring of the switch in which the plug is inserted and thence to the tip of the plug
and thence through the condenser to the tip of the answering plug of the pair, the
condenser being charged by the test battery when the connection is first made the
test battery will be shut off from the tip of the connecting plug at the condenser.
Voice currents, may, however be sent through the condenser; thus by throwing the
loop key in proper position the operator's telephone will be brought into circuit with
the calling subscriber and the order of the calling subscriber may be received by the
operator. The operator having received the order at once applies the tip of the
connecting plug to the test piece of the line called for. As before stated the test
battery with respect to the circuit of the calling subscriber's line, is shut off from the
tip of the connecting plug at the condenser. Therefore if there be no current present
from some other source at the test piece to which the tip of the plug is applied, there
will be no sound heard in the operator's telephone when thus connected therewith for
the reason that the operator's telephone is connected with the strand of the cord'
which connects to the tip of the connecting plug at a point between the condenser and
the said strand, even though the line tested were a single wire circuit having its test
pieces connected together and through resistance to ground. Therefore, the operator
making the test and hearing no sound will know that the line is free; on the other
hand if the operator hears a click in her telephone when the test is made she will
know that battery is connected with the test circuit of the line called for and this will
indicate that the line is busy.
My Invention is illustrated in the accompanying drawings in which
Figure 1 is a diagram illustrative of three telephone lines, two metallic and one
single connected with three different switch boards at the central office in connection
with the operator's apparatus and circuits at two of the boards embodying my
Invention.
.
Figure 2 is a detailed view of the circuits of a single pair of cords, the springs and
contacts of the loop switch connected therewith being shown in perspective.
Figures 3 and 4 are elevations of the different sides of the cam lever loop switch in
detail.
Like parts are indicated by similar letters of reference throughout the different
figures.
I will first describe the operator's apparatus as illustrated in Figures 2, 3 and 4.
The answering loop plug a is shown inserted in a switch; the other plug of the pair
is shown with its tip touching a test piece as in the act of testing. The circuit
between the tip of the plugs 6 and a may be traced as follows:-From the tip of the
plug by strande to calling key d; thence to contact e and spring of the switch,
thence through the condenser g to contact of the switch and thence to spring i of
the switch, and thence to the other calling key k and thence to the tip of plug a.
The circuit between the sleeves of the plugs may be traced directly by strand. The
ground branch m is permanently connected through a self induction coil with the
strand while the branch n is permanently connected with the strand 7 through a
self induction coil and test battery o. The self induction coits are inserted to block
the passage of rapidly varying electric currents either from or to the line. Between the
condenser and the spring of the switch a ground circuit or branch is provided
which passes through the operator's telephone, thus connecting the telephone with
the strande when the switch is in the position shown. From the strand / a
branch connects with the contact pl and spring p² of the switch, spring p² being
permanently connected with a self induction device p³ included in a ground circuit.
When the telephone is connected with strand c the corresponding self induction
device por dummy telephone set as it has been sometimes called, in the United
States, is connected in a similar manner with the strand 1. When the lever
of

page_text: the switch is thrown down the connections of the springs are changed, the springs f
and p being separated from their contacts ep respectively, while spring i is at the
same time disconnected from its contact and closed to its lower contact gl. In
this manner the telephone as well as the corresponding dummy set may be discon-
nected from the strands of the cord and the portion of the operator's telephone
circuit containing condenser g cut out, the circuit of cord, c, however being com-
pleted through the clearing out shutter ³, contact q' and spring i direct; thus
when the lever is thrown down we have direct circuits through the strands of the
cords; the cord being, however, provided with the ground connection n through
the self induction coil and test battery o, while the other cord c is provided with
the connection m through a similar self induction coil. The calling keys d, k
are of the usual construction; by depressing key d current will be sent over the
circuit connected with the tip of plug b, while on depressing key k current will be
sent from the generator over the circuit with which the tip of plug a may be con-
nected. It will be seen that the switching device operated by lever q consists of
three springs fi p². The cam at the lower end of lever is placed in position to
force the springs fand p² away from contacts e, p respectively and at the same time
separate spring i from contact hand close the same upon contact g' when the lever is
thrown forward. When the lever is up, the springs, by their own tension are brought
to the positions shown in Figures 2, 3 and 4.
Referring now to Figure 1 it will be seen that telephone liner extends in two
branches or limbs to the central office, the limb being connected through the
springs of the switches on the different boards and from the contact of the
to ground. Limb r is connected with
switch through the individual annunciator
the frames or test pieces of said switches 73 pt.
The single wire circuit extends from the subscriber's station thereof through the
springs and contacts of the switches 787 7.10 and from the contact of switch 10
through the individual annuciator to ground: the rings or test pieces of
switches 10 are permanently connected together by test wire 12 said test
wire instead of extending back to subscriber's station as is the case with respect
to metallic circuits-is
-metallic-circuit 1 connected directly to ground-through: resistanco=713 he
from the subscriber's station thereof in two branches
through switches 18 16 and 17, the same as described with respect to metallic circuit r,
the individual annunciator 71s being included in the limb or branch which passes
through the springs and contacts of the switches.
The operator's apparatus at the last board I have lettered to correspond with the
lettering of Figure 2. Similar apparatus is provided at the first board, the pair of
plugs a being shown inserted in spring jacks 2 respectively to switch the tele-
phone lines together. The cam lever is thrown up and the operator's telephone
at the first board is disconnected froin the united circuits of the two lines, while the
clearing out annunciator is included in the circuit. The test battery is connected
to the strand which connects together the sleeves of the plugs a b'. The
resistance in the test circuit 12 is so great that only a small amount of current will
pass from the battery o to ground through said resistance 71. We will suppose that
when two wires are thus connected upon one board, one of the connected lines is
called for at another board, as for example, at the last board. Let the signal be sent
in over metallic circuit to throw down the shutter 18 at the last board as shown,
the operator seeing the shutter of annunciator fall, inserts answering plug a into
the spring jack and throwing down the lever q brings her telephone into circuit,
and is in position to receive the order. The order being received, we will say for con-
nection with liner said liner is tested by means of the connecting plug b applied to
the test piece of switch as shown. As line is already connected at another board,
the test battery o will be closed to the tip of plug b when applied to the tip of the
frame of switch and the operator listening at her telephone will hear the sound
which is due to the closing of the circuit. The circuit thus formed may be traced
from battery o to the strand of the cords at the first board and thence to the sleeve
of the plug a' thence to the frame of switch and thence to the frame of switch r
2"

page_text: i
thence to the tip of plugib, thence to the strande connecting the tips of the cords, and
thence through contacte, and spring f of the switch and thence through the operator's
telephone to, ground! The operator listening at the telephone and hearing the sound
will know that the line tested is busy. Suppose the single wire circuit were asked
for instead of the metallic circuit rin this case, the test would be made at switch
and the circuit thus formed from the test battery might be traced to strand of the
cords at. the first board, thence to the sleeve of plug. 6 and thence to the tip of
plug, and thence, through the strande to keysk; thence to contacte spring, and the
telephone to.ground.
If the condenser.g were not included in the circuit a false signal would be heard in
.the operator's telephone on testing an idle single circuit telephone line as circuit?.
Thus, as shown, at the last: board the answering plugaas is inserted'in spring jack
switch. Tracing, from battery.o the circuittis complete to the sleeve of plug a,
thence to the frame of switch randithence over circuit through the subscriber's
station and back, to the spring of switch thence to the tip of plug a thence to
spring i of the switch and contact hand thence through the telephone to ground. Thus
omitting the condenser a complete circuit is formed from battery through the
operator's, telephone. Now on applying the tip of the connecting plug to the
frame of a switch of a single circuit liue, a third leg or half connection would be
formed to ground through resistance 7¹³. The closing of this branch to ground would
change the electrical condition of the telephone, and cause a sound' therein which
could not be distinguished from a true busy signal. Thus without the condenser there
would be no sure means of: determining whether a single line called for by a metallic
circuit subscriber was busy.
"
Each operator may have, say fifteen pairs of connecting cords; consequently fifteen
switches. Of those switches the different springs are connected together and to
the ground, branch including the operator's telephone. Spring i is connected only
to its particular strand of a pair of cords.
These contacts or all of each operator's switches whatever the number may be,
are connected together, and to the wire connecting with one side of the condenser
as shown. Springs 3 of these switches are connected together; and to the ground
branch including the dummy telephone set p³ thus it will be seen that only one
condenser is required for each operator's outfit.
My Invention admits of various modifications which would readily suggest
themselves to those skilled in the art, and I. therefore do not limit my Invention
.to the construction shown.
.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be performed.I declare that, what! I
claim is -
,
1. In a system of testing, to. determine whether a subscriberis linc. is in use at
another section. of switch. board or not, the use of a retardation coil, con-
nected from the subscriber's lines in a derived circuit, either direct or through' a
.battery to ground.
2. The combination with a metallic circuit telephone line, connected with switches
on two or more switch boards, one branch of said metallic circuit being normally open
at the central, office and the other branch being normally connected through an
individual annunciator to ground of a single wire circuit.connected with switches, one
on each of the switch boards and through an annunciator to ground, the frames 'or
test pieces of the switches of said single line being connected together and through
resistance to ground, and operator's apparatus consisting of a pair of loop plugs, and
the cords connected therewith, one strand of said cord being connected with a ground
branch containing a self induction coil and extending, from the connection with' said
branch through one spring and contact of a switching device, thence through a con-
denser to another ground branch; containing.a telephone and thence through another
spring and contact of said switching device, the other strand of said pair of cords
being, connected, with a ground. branch including a test battery and self induction

page_text: coil, whereby the two telephone lines may be tested and connected together, substan-
tially as and for the purpose specified.
3. The combination with a metallic circuit telephone line connected with switches,.
on two or more switch boards, one branch of said metallic circuit being normally open
at the central office and the other branch being normally connected through an
individual annunciator to ground of a single wire circuit connected with switches,..
one on each of the switch boards, and through an annunciator to ground, the
frames or test pieces of the switches of said single line being connected together,.
and through resistance to ground and operator's connecting, switching and testing
apparatus, whereby the two telephone lines may be tested and connected together,.
substantially as and for the purpose specified.
4. A metallic circuit with the answering plug of a pair inserted in a spring
jack switch of the line upon one of two or more switch boards, with which the line is.
connected, the single circuit line connected with the same switch boards, the frames.
or test pieces of the switches of said single circuit line being connected together and
through resistance to ground, the answering plug of said pair being applied to the ring
or test piece of the switch of the single circuit line on the same board with the switch.
of the metallic circuit in which the answering plug is inserted a test battery connected
with the strand of the cord which unites the sleeves of the plugs, a condenser included
in the circuit of the other strand of the cords and a telephone in a ground branch
connected with said strand, the connection with the telephone being on the side of the
condenser nearest the connecting plug, whereby current from the test battery is.
prevented from passing through the test circuit of the single line to ground, substan-.
tially as and for the purpose specified.
Dated this 16th day of May 1890.
J. E. KINGSBURY.