Improvements in Telephonic Systems and Apparatus.
Year: 1898

page_text: Date of Application, 30th Aug., 1898
Complete Specification Left, 29th May, 1899-Accepted, 30th Sept., 1899
PROVISIONAL SPECIFICATION.
Improvements in Telephonic Systems and Apparatus.
I, JOHN EDWARD KINGSBURY, of 79, Coleman Street, in the City of London,
Manager, do hereby declare the nature of this invention (which has been com-
municated to me from abroad by The Western Electric Company, of Chicago,
Illinois, United States of America,) to be as follows:-
This invention relates to improvements in the circuits and apparatus aiming to
better the transmission and receiving of the sub-stations and to better the
working of the central station described in the prior Specification No. 8222, of
the 25th April 1895, in which the transmitting telephone is supplied with
current from a central source.
A transmitter for use in circuits of considerable resistance must itself have a
resistance which is dominating in the total resistance of the circuit and must be
capable of varying its resistance between very wide limits.
A good transmitter is obtained by removing about two thirds or three fourths
of the granular carbon from an ordinary solid back instrument. Such a trans-
mitter will have a resistance, when quiet, of something over 100 ohms, and will
vary from 20 to 1500 ohms. when in use.
The sub-station condenser circuit for common battery transmitters shown in
Figure 1 has the advantage of avoiding the booming sound of transmitters not
provided with a circuit for localizing the variations of current. The receiving
telephone is put in the local circuit with the condenser by which both trans-
mission and receiving are improved. The circuit is arranged to employ a single
condenser in circuit with the bell at one time and in circuit with the transmitter
at another time. Modifications of this circuit are shown in Figures 2, 3 and 4.
Figures 5 and 6 show the improvements of the switchboard devices for uniting
lines of different character, comprising metallic and grounded circuit lines, and
metallic lines with permanent ground branches; the object of the invention being
to attain a uniform operation of the signals, independent of the character of the
lines with which they are associated.
My correspondents give also as an improvement, means to charge the storage
battery which forms the source of supply of the exchange while it is in use, or,
in other words, to supply the current directly from the dynamo, maintaining the
charged storage battery across the supply circuit for use at night and for reserve
in case of failure of the dynamo. The noise of the commutator of the generator
has until now prevented this practice, but we give herein two two expedients which
are available. One of these consists in putting low resistance impedance coils
in the mains of the generator; the other and preferable method consists in so
subdividing the commutator and running the commutator at a high speed so
that the number of pulsations from the commutator exceeds six or eight thousand
per second, at which point the noise from the commutator becomes inaudible.
Figure 1 shows an improved scheme of circuits for receiving and transmitting
telephones in systems in which the transmitter is supplied from a central source
with current. The receiving telephone is placed in a shunt circuit around the

page_text: transmitting telephone whereby an increase of efficiency in transmitting telephonic
currents is attained through the removal of the impedance and resistance of the
receiving telephone from the line circuit.
Figure represents two telephone lines, 1, 2, and 3, 4, which are assumed to
be connected in a telephone switchboard. In the switchboard, which is also a
point from which the lines receive their current supply for exciting the trans-
mitter, the line circuit is furnished with a bridge or cross conductor 5 which
includes a source a of current, together with windings and 6 of impedance coils
for preventing the shunting of telephonic currents through the bridge.
The substation is equipped with a receiving telephone c, a transmitting tele-
phone d, and induction coil e, having four windings and a condenser f.
"
The line circuit may be considered as being complete through winding e¹,
transmitting telephone d, and winding of the induction coil. About the trans-
mitting telephone a shunt current 6 is arranged which includes serially a
winding of the induction coil, the receiving telephone the condenser f and
the winding of the induction coil. The windings e¹ and e³ should of course tend
to magnetize the core in the same direction when traversed by current, and
windings and should have similar relation to each other. Windings e
and should be so related to windings that they tend to magnetize the core
in the same direction as if they were traversed serially by a continuous current.
A steady current flows from battery a in the central office through both lines
to the substations thereof, finding circuit at each substation through the wind-
ing e transmitting telephone d and winding e of the induction coil. An increase
in the resistance of the transmitting telephone d at a station tends to diminish
the currents through the windings e¹ and e³ and for an instant diverts the currents
through the shunt 6 which charges the condenser f; the current flowing through
windings and et is then in proper direction to induce an electro-motive force
in windings e and etending to still further diminish the current there. A
subsequent decrease in the resistance of transmitter & permits an increased current
to flow in the line circuit at the same time permitting the discharge of con-
denser f; this discharge takes place through windings and e in proper direction
to accentuate the increased flow through windings e¹ e. Sound waves striking the
transmitter d therefore set up in the line circuit an undulating current whose
undulations are greatly amplified by the inductive action of the condenser f
acting through the windings and e. When the receiving telephone e is of
usual construction, the condenser f may be of two microfarads capacity, under
which conditions the impedance of the receiving telephone appears to have no
deleterious effect in the shunt circuit.
Indulations created in the line wire 1, 2, are not propagated through the bridge 5,
at the station of current supply, on account of the presence in the bridge of the
impedance coils 1, but traverse the line conductors 3 and 4 to the distant
station. This current is substantially an alternating current, which finds free
circuit through the condenser f and the receiving telephone c.
C
The efficiency of the system in receiving telephonic currents is in no wise
impaired by placing the receiver c in the shunt circuit 6 instead of the direct line
circuit, while the efficiency of transmission is greatly increased by eliminating the
impedance of the receiver from the line circuit; and the resistance of the circuit
to the exciting current is diminished.
Figure 2 illustrates two similar substations A and B which are assumed to be
connected together at a telephone switchboard, through a repeating coil having
four windings and a common source of current. Each substation comprises a
high resistance bell a, a, permanently conected on the line in circuit with a
condenser g, g¹.
When the receiver h, h¹, is on the hook, the switch k, k¹, is not in connection
with the points m¹, m³, and the calling current from the central station flows
through the lines 1 and 2 through the bell a, a¹, actuating it, and through the
condenser α. a¹.

page_text: When the receiver is off the hook, the switch k, k¹, makes connection with the
two points m, m2, thereby connecting the transmitter d, d, through the primary
winding of the induction coil e, e¹ and by conductor 5 in bridge with the
lines 1 and 2: and at the same time closing the shunt circuit through the
secondary winding of the induction coil f¹, the conductor 6, the receiver h, h³,
the condenser, g, g¹, the transmitter d d and the switch k, k¹.
Figure 3 shows the scheme of a practical mounting of a substation. Figure 4
shows how the substation may be changed to work with a local transmitter battery,
without interfering with the other regular features of the common battery
system.
In the scheme shown in Figure 3, when the receiver is on the hook the primary
or the line circuit is from terminal L by conductor 5 to condenser a, thence by
conductors 6 and 7 to bell b through conductor 8 to earth.
When the receiver is off the hook the primary or line circuit is from terminal L¹
by conductor 13 to terminal 1, through the primary winding of the induction coil
to terminal 2, thence via conductor 14 to the contact point f, which is now in
connection with switch e, thence by conductor 11 to the transmitter d and over
conductor 12 to terminal L³. The shunt circuit is from terminal L² over con-
ductor 5 through condenser a over conductor 6 to terminal 3, through the secondary
winding of the induction coil to terminal 4 over conductor 9, through the
receiver c, over conductor 10, to contact f¹, which is now connected to switch e,
thence by conductor 11, through transmitter d and by conductor 12 to L³.
Terminals B and B are left spare and conductors 15 and 16 are not in use.
Figure 4 shows by dotted lines how the modifications for working with a local
transmitter battery may be made. The local transmitter battery is connected
between terminals B and B the induction coil is removed and a connection made
between the terminals 1 and 4 and an ordinary transmitter with its own induction
coil is provided in place of the common battery transmitter.
The ringing circuit remains the same as described in connection with Figure 3.
When the receiver is off the hook the line circuit is from L' by conductor 13 to
terminal 1, thence by conductor 13" to terminal 4, then via conductor 9, receiver c,
conductor 10, contact f¹, switch e, conductor 11, through the secondary winding
of the induction coil and conductor 12 to terminal L2. The local circuit is
from one pole of the transmitter battery to terminal 13 thence over conductors 15
and 14 to contact f, switch e and conductor 11, through the primary winding of the
induction coil and transmitter d thence via conductor 16 to the other pole of the
local battery.
The present invention applies also to improvements in the circuits and opera-
tion of supervisory signals in connection with metallic circuits having permanent
ground branches, with metallic circuits free from such ground connections, and
with grounded circuits, indifferently. It consists in the combination with the two
conductors forming a plug circuit or link for uniting telephone lines, of a source
of current in a bridge of the plug circuit, an electro-magnet in each of the link
conductors and a signal controlled by these magnets jointly, the signal being
preferably concealed when both magnets are excited; and as respects the use of
these appliances with grounded lines, it further consists in a normal partial
return conductor, to excite one of the signal controlling magnets during connection
with the line.
The features of this improvement are shown diagrammatically in Figure 5.
This drawing represents the apparatus of three substations with a grounded line
extending from a central office to one of the stations, and a metallic circuit party
line extending from the same office to the remaining stations, together with
plugs and a plug circuit and other apparatus in accordance with this invention for
uniting the lines and supervising the use of the circuit thus established in the
central office.
Each substation is furnished with transmitting and receiving telephones, a
call bell and a telephone switch for closing the line circuit through the telephones

page_text: during the use of these instruments. At the station of the grounded line, the
line conductor 1 is provided with two paths to the grounded return conductor 2,
one of which includes the polarized call bell a together with a condenser a
and the other of which traverses the telephones a² and a3 and is controlled by
the telephone switch a. The rising of the switch when relieved of its weight
of the receiving telephone, thus closes the line circuit as respects continuous
or unvarying current.
The apparatus at the station A' and A2 of the party line are of like character,
but are somewhat differently arranged in the circuit. At each station a bridge 3
of the line circuit 4, 5, exists controlled by the telephone switch a³, which
includes the transmitting and receiving telephones; but at the station A¹ the
bell a is located in a ground branch 6 from the line conductor 5, no condenser
being interposed in this circuit, while at the station A2 the bell a is similarly
located in a ground branch 7 from the line conductor 4. This arrangement of
the bells is to permit the selective operation of the bells at the different stations;
it being obviously possible to send a calling current over one line conductor and
the ground return to ring the bell at station A¹, or over the line conductor and the
ground return to ring the bell at station A².
The line circuits of whatever nature are led to the line contacts of spring
jack bin a telephone switchboard, thence normal extensions are led through the
switch contacts of a cut-off relay c to sources of current and individual or line
signals of special arrangement in accordance with the nature of the line.
Thus the extension of the line conductor 1 is led through the magnet winding
of a relay d to the pole of a battery e or other source of current. It is customary
to provide also the wire 2 which forms within the switchboard the return circuit
for the line this wire is connected with one contact piece of the spring-jack b
ald is then grounded, usually at a point outside of the switchboard. In con-
verting such a grounded line into a metallic circuit the portions of wire 2 at the
substations and at the central office are disconnected from earth and united by
an insulated wire, and the wire 2 is extended to the contact anvil of cut-off
relay c.
In carrying out this improvement however, I interpose a battery f of small
voltage in a grounded conductor 2 at the central office, for a purpose which will
be explained hereinafter. The relay controls a local circuit 8 which includes
a secondary line signal, which may be a small incandescent lamp, placed near
the springjack of the line in the switchboard. The cut-off relay following the
usual practice is located in a conductor 9 grounded at one end and terminating
in a normally open contact ring 61 of the springjack of the line.
The party line is similarly provided with a secondary line signal controlled
by the relay and is connected with a source of current e; but in this instance
the normal ground extension of line conductor 4 includes the magnet winding of
the relay d, while the source of current e is interposed in the grounded exten-
sion of the other line conductor 5. The purpose of this arrangement is to permit
the excitement of the relay only when a connection is completed between the
line conductors at one of the substations.
•
The apparatus for uniting the lines in the switchboard comprises plugs g and gl
cach with three contacts designed to register with the three contact parts of
a springjack, circuits uniting the line contacts of the plugs to form the plug
circuit, and other local conductors terminating in the local contacts
of the plugs to bring about the operation of certain appliances in
the switch board. Thus the spherical tips of the plugs are united
by conductor 10, while the short rings, constructed to register with the
longer springs of the springjacks, are united by a conductor 11. The con-
ductors 10 and 11 of the plug circuit traverse the windings of the repeating coil h,
two serially connected windings of the coil being interposed, in each conductor;
the points of junction of these windings are united by a bridge 12 of the plug
circuit, which includes a source of current. The pole of this source of current

page_text: adjacent to conductor 10 is grounded. The plug circuit traverses the switch.
contacts of the usual calling keys k, and for looping a generator of signalling
current into circuit with plug g' to send calling current over either or both of
two line wires; it is connected with an operator's listening key for bringing
a telephone into the plug circuit.
The sleeve contacts of the plugs, which register with the ring contacts of the
spring jacks, from the terminals of conductors 13 and 14, respectively, which lead
to the free pole of a grounded battery m, and which include signals n and n¹.
The different signals n and n' refer to the corresponding plugs 9 and g¹, being
associated with them in the switchboard; their display is determined by the
application or withdrawal of shunts which are controlled by relays in the plug
circuit. The disposition of these relays in the plug circuit, and the arrange-
ment of circuits by which they control the supervisory signal lamps n and n¹,
to produce a uniform operation of the signals when the plug circuits are used in
uniting lines of diverse types, constitute the essential features of this invention.
The controlling relays for the signal n are designated and p, the former is
included in the portion of conductor 10 between the bridge 12 and the plug g,
and the latter in the like portion of conductor 11. The relays o¹ and p¹ in
a like manner control the signal n¹ referring to the plug gl, the former relay
being in the portion of conductor 10 leading from the bridge to the plug gi,
and the latter relay being in a like part of conductor 11. The shunt through
the agency of which the relays
o and
control the signal n consists in the
wire 15 which traverses in series the switch contacts of the two relays and p;
this wire may include a coil of low resistance, the diversion of the full current
from the signal lamp being unnecessary. A like shunt for the lamp n¹ exists in
the wire 16, whose continuity is controlled at two points by the relays. o¹
and 2.
The act of calling for connection from a substation is the same in all stations;
it consists merely in taking the telephone from its switch for use. The mode
in which this act causes the display of the line or calling signal, however varies
in the case of grounded lines and party lines. Thus the removal of a telephone
from its switch at the station A produces a closed circuit through the telephones
at that station which permits current to flow from battery e through the magnet
winding of relay d, over the line conductor 1 to the substation, and thence by way
of the return conductor 2 to earth, whereby the local circuit including the
secondary signal is closed and the signal lamp is lighted. In calling from a
station A or A2 the closure of the circuit through the telephones by the telephone
switch permits current to flow from the battery e of the party line through the
conductor 5, thence through the bridge including the telephones, returning to
the central office through conductor 4 of the line and traversing the magnet
winding of relay d. It will be noted that the battery has normally no circuit
through the relay, notwithstanding the existence of the permanent ground
connections with the line.
In response to the display of a line signal of any line, the attendant will insert
the plug into the spring jack associated with the signal, and will bring her
telephone into connection with the plug circuit to learn from the calling subscriber
the order for the line with which connection is required. After receiving the
information she will insert the plug ginto the spring jack of the line called for,
as that of the lines to station A' or A2; after which she will ring the bell at
the required station, by means of a key k if the line be a single station line, or
through the instrumentality of the proper key or if the line be a party
line, in accordance with well known methods.
The insertion of plug into the spring jack b of any line closes a local
circuit made up of conductors 13, 9, in which current is thus permitted to flow
from battery m to excite the supervisory lamp signal n and the cut-off relay c.
The cut-off relay severs the normal ground connections of the line and leaves the
line in closed circuit with the plug circuit; and through the medium of this

page_text: circuit with the line to the required station. The presence of plug g in th
spring jack of the line called for similarly closes the local circuit 14, §
of the line called for, whereby the signal lamp n is excited and the cut-off rela
of the answering line is energized and severs the ground connection of the latte
line. The functions of the parts thus far described are performed in this wa
in the case of any connections, whether they be with grounded or metallic circuits
or with metallic party lines. The behaviour of the relays o and p and o' pi
dependent on the nature of the lines with which they become associated, however
and must be traced in different cases.
When the calling line is, as has been described, a grounded line, the ac
of answering a call brings the battery i into circuit with the line 1, 2, which
is closed at the station, whereby current is permitted to flow through the
conductor 11, traversing the winding of relay p, to the line wire 1, and
thence to grounded return conductor 2 at the substation; at the same time
current is produced by the battery in the grounded conductor 2 at the central
office to the conductor 10 of the plug circuit, and thus to earth through the
magnet winding of relay o. Magnet o is thus excited by the current which will
ain constant while the connection exists, while magnet 2 becomes excited
current dependent on the position of the telephone switch at the calling
station. Relay o closes the break in the shunt wire 15 which it controls, and
maintai
continuity of this wire during the existence of the
magnet similarly closes the break which it controls while the telephone switch
is in its alternate position, the telephone being in use. The shunt wire is thus
effective in diverting current from the lamp n, so that this lamp remains dark
while the telephone at the calling station is in use, but becomes lighted whenever
the telephone is replaced on its switch.
334
Turning now to the operation of the relays o' and p²; The insertion of plug g¹
e spring jack of the party line provides a circuit from battery i through
portions of conductors 10 and 11 of the plug circuit to the wires 5 and 4 of
the line circuit. Current will flow from conductors 11 and 4, through the
ground branch 7 at the substation including the bell, which may excite the
relay p, and may cause this relay to close the break which it controls in the
shunt wire 16; but no current will exist in the portion of conductor 10 which
includes the winding of relay o¹, since no source of current is found connected
with the portions of the plug circuit and line circuit which are directly connected
with this instrument; hence the shunt wire 16 will remain broken at the switch
contacts of relay o¹, and the lamp n', being not shunted, will remain lighted.
Its illuminated condition constitutes an indication to the operator that the
subscriber at the station called has as yet made no response. When the telephone
is taken for use at either station A¹ or A2 a bridge of the line circuit is closed at
that point, as already mentioned, so that a complete circuit is formed from
battery i through a portion of conductor 11, line wire 4, line wire 5, a portion of
conductor 10, returning thence to battery i; the current in this circuit excites
the magnet of relay o which closes the second break in the shunt 16, and thus
brings about the extinction of lamp n'. This signifies to the attendant a
response to the call at the station called.
It will be apparent that if the called line were a grounded circuit, the relays o¹
and would be operated in the way traced for the relays o and in making
connection with the calling line. If the called line were a metallic circuit the
operation would be similar to this just described for the party line, the two
relays being excited by current passing out over one line wire, finding circuit
through the bridge closed in the telephones, and returning through the other
line wire to excite the second relay in the plug circuit. In general, each signal n
and n will be caused to indicate, by its lighted or dark condition, the position
of the switch at the station of any line with which it may be connected, irre- 5
spective of the nature of the line circuit.
The accompanying Fig. 6 illustrates another improvement.
This figure

page_text: represents two telephone lines one a grounded special circuit and the other a
metallic party line circuit with grounds at different stations containing selective
calling appliances, together with signalling and switching apparatus for the lines
in the switch-board, the party line circuit being equipped with a device for
maintaining the normal operation of the supervisory signals in accordance with
the present invention.
All the substations of these lines are furnished with the usual receiving and
transmitting telephones a and a¹, telephone switches a² for closing bridges of
the line circuit through these instruments in the use of the telephones, and
polarized call bells a. The bell at station A is located in a bridge or ground
branch from the line together with a condenser at which interrupts the con-
tinuity of the line as to the battery currents made use of in signalling to the
office, while being complete as respects the alternating calling current for ring-
ing the bell. The single conductor 1 of this grounded circuit is led to the line
contacts of the spring jack b in the switch board, from which it is prolonged
through the switch contacts of a cut-off relay c and through the magnet winding
of a signal controlling relay d to one pole of grounded battery e. The relay d
controls a secondary line signal d' associated with the spring jack b in the switch
board, through the agency of a normally broken local circuit 2, which it com-
pletes when excited. The actuating magnet of the cut-off relay c is connected
in a local grounded conductor 3 which terminates in an insulated contact ring of
the spring jack b.
At each of the stations A¹ and A2 of the party line the bell a³ is connected in
a permanent ground branch from one of the line conductors-the bell at
station A being in a ground branch 4 from line conductor 5, and the bell at
station A being in a ground branch G from line conductor 7. The line conductors
lead, like that of the grounded line, to the line contacts of a spring jack in
the switchboard, from which they are extended through the switch contacts of
a cut-off relay c to earth and to the pole of a grounded battery e, respectively;
the magnet of the signal-controlling relay d is, however, included in the
extension of line conductor 7, so that current reaches the magnet only when a
bridge of the line is closed through the telephone at one of the stations.
In the switchboard the usual pairs of connecting plugs f and flare provided
for the use of the operator in uniting lines. Like line contacts of the plugs are
connected together through conductors 9 and 10 which constitute the plug circuit,
the usual calling keys and g¹ being interposed in the conductors of the plug
circuit, and the listening key h being connected therewith for bringing the
telephone into a bridge of the plug circuit. It will be noted that one of the
calling keys is adapted to apply one pole of a grounded source i of calling
current to one line conductor 7, to ring the bell a³ at station A2, while the other
key is adapted to apply the same pole of the source of calling current to the
other line conductor 5 to ring the bell at station A'; the key g', however, when
it applied calling current to the line wire 5, also connected with the line wire 7
one pole of a grounded battery k, for a purpose which will be hereinafter set
forth.
The conductive continuity of the plug circuit 9, 10, is broken by interposing
in cach conductor thereof two serially connected windings of a repeating coil 1,
in a well known way; the points of junction of the windings of these coils are
led to the poles of the battery k, which thus may serve for supplying, current to
the substation transmitters, if desired, as well as for operating supervising
signals associated with the plug circuit.
The conductor 10 of the plug circuit leading to each of the plugs traverses the
magnet winding of a supervisory relay, these being designated m and m
respectively. Each of these magnets controls the display of a supervisory signal,
the signals being marked n and n¹, associated with the corresponding plug for f.
The signal lamp n is included in a branch 11 from a grounded battery o to the
contact sleeve of plug f which is adapted to make connection with the test ring

page_text: of the spring jack b. Lamp is likewise included in a wire 12 leading from
the same battery to the corresponding part of plug fl. The relays m and m
control these signals and n' through the agency of shunts 13 and 14, respec-
tively, which are completed when the relays are excited. These signals are
of usual and well known character in telephone exchanges. When a connection
is established between lines in the switchboard, it is intended that current shall
flow from battery k through the conductors 9 and 10 of the plug cfrcuit to each
line, the existence of the current being determined by the condition of the bridge
including the telephones at the substation of the line. A supervisory relay m
or m is in the path of current to each of the lines; when the relay is excited by
current flowing in the line with which it is temporarily associated, it is designed
to close the shunt about the signal lamp, and thus to divert therefrom current
flowing in the local circuit completed in the act of making connection, to render
the lamp dark. Thus each supervisory signal lamp is to remain dark while the
telephone of the station with which it is in temporary association is in use,
being lighted when the bridge at the station is broken."
In providing for the uniform operation of these supervisory signals on
grounded metallic circuits like that leading to stations A1 and A2, I place in the
line conductor 7 of the line the magnet of a relay p. This magnet may be of
moderate resistance, and should preferably be shunted by a non-inductive
resistance to furnish a free path for telephone currents. This relay is responsive
to currents in the conductor 7, which, however, can occur only when a com-
plete path is established from line conductor 5 through a bridge at one of the
stations A or A2. The switch contacts p 22 of this relay control the continuity
of a conductor 15 leading from the free pole of battery k to the line conductor 5.
In order to trace the operation of the supervisory signals, and the control of
the signal associated with the party line through the agency of magnet p, let
a connection be assumed to originate at station A, to be extended to station A¹.
The removal of the telephone from its switch at station A permits current to
flow from the battery e which excites the relay d and brings about the display of
the line signal d¹ in the switchboard. Answering the call, the operator inserts
plug into the spring jack b, at the same time bringing her telephone into the
plug circuit to learn the order. The insertion of the plug in the spring jack
completes a local circuit of battery o through wires 11 and 3, wherein current
excites the cut-off relay c and causes this appliance to sever the normal ground
connections of the line. At the same time current is permitted to flow from
battery through the portion of the plug circuit connected with the calling
line, over the line conductor, and through the telephones at the station to earth,
whereby the supervisory relay m is excited and closes the shunt about the super-
visory lamp n. Upon learning the subscriber's order, the operator inserts plug, f¹
into spring jack 6 of the line 5, 7, and depresses the key g¹ to ring the bell at
the station A¹. The insertion of plug f¹ in the spring jack 6 completes a local
circuit 12, 3, which includes the signal lamp n' and the magnet of cut-off relay c
of the called line. The cut-off relay severs the ground connections of the line
in the exchange, and the lamp n becomes lighted. The depression of the
key g connects one pole of the source of alternating calling current with the
line conductor 5, from which the current finds circuit to station A¹ and through
the ground branch 4 to earth, ringing the bell at that station; it also applies
one pole of battery to the line conductor 7, whereby a current is produced
through relay p, reaching earth through the ground branch 6 at station A³,
which excites the relay and breaks the conductor 15 leading to earth from line
wire 5 in the central office.
Having transmitted the specialized call to call the desired station, the operator
releases the key g¹. A circuit exists from battery through a portion of con-
ductor 10 of the plug circuit including the supervisory relay m¹ to line wire 5
and thence through the ground conductor 4 at station A¹, but as soon as the
relay p becomes inert a short circuit is formed from battery k through wire 15

page_text: to the line wire 5 in shunt of relay m¹, whereby the latter is deprived of current
and caused to maintain the break in the shunt about signal n¹. Hence the
supervisory signal n¹ remains lighted to show that the called party had not
responded. The taking of the telephone at station A¹ in response to a call
closes a bridge of the circuit at that station, whereby current is permitted to
flow over line wire 5, through the bridge including the telephones at station A¹,
returning through the line wire 7 including the magnet of relay p, through a
portion of conductor 9 of the plug circuit, to earth, in the central office. This
current excites the relay p which breaks the short circuit 15 and diverts current
through the relay m¹; this latter appliance, becoming excited, closes the shunt
about lamp n' and thus brings about its extinction. The darkening of the
lamp n is a signal to the operator that the call to station A¹ has received
attention.
It will be apparent that the replacement of the telephone upon the switch at
either station, by breaking the bridge closed through the telephone at the station,
will deprive the corresponding supervisory relay of current, and thus cause the
lighting of the corresponding lamp n or n¹; this result being attained directly
in the case of the grounded line, but indirectly through the agency of relay ?,
in the case of the grounded metallic circuit line. The display of both signals
may be accepted by the attendant as a call for disconnection.
The nature of the controlling device will be dependent on the nature of the
line with which it is associated; both its character and the means by which it
controls the supervisory signal to compensate for the special nature of the line.
to bring the operation of the supervisory signals in connection with the line
into harmony with their operation in association with other lines, may be
varied to a considerable extent. In general, the last described improvement
contemplates broadly the provision of a device for each line of special nature
which responds to some predetermined act at a station of the special line, and
which in its response, controls the supervisory signals to make them operate in
the way usual with lines of ordinary character.
Improvements in Telephonic Systems and Apparatus.
I, JOHN EDWARD KINGSBURY, of 79, Coleman Street, in the City of London,
Manager, do hereby declare the nature of this invention (which has been com-
municated to me from abroad by the Western Electric Company, of Chicago,
Illinois, United States of America,) and in what manner the same is to be per-
formed to be particularly described and ascertained in and by the following
statement:-
This invention relates to improvements in the circuits and apparatus aiming
to better the transmission and receiving of the sub-stations and to better the
working of the central station described in the prior Specification No. 8222, of
the 25th April 1895, in which the transmitting telephone is supplied with cur-
rent from a central source.
The drawings referred to are those left with the Provisional Specification.
A transmitter for use in circuits of considerable resistance must itself have
a resistance which is dominating in the total resistance of the circuit and must
be capable of varying its resistance between very wide limits.
A good transmitter is obtained by removing about two thirds or three fourths

page_text: of the granular carbon from an ordinary solid back instrument. Such a trans-
mitter will have a resistance, when quiet, of something over 100 ohms, and will
vary from 20 to 1500 ohms when in use.
The sub-station condenser circuit for common battery transmitters shown in
Figure 1 has the advantage of avoiding the booming sound of transmitters not
provided with a circuit for localizing the variations of current. The receiving
telephone is put in the local circuit with the condenser by which both trans-
mission and receiving are improved. The circuit is arranged to employ a single
condenser in circuit with the bell at one time and in circuit with the speaking
apparatus at another time. Modifications of this circuit are shown in Figures 2,
3 and 4. Figures 5 and 6 show the improvements of the switch board devices
for uniting lines of different character, comprising metallic and grounded circuit
lines, and metallic lines with permanent ground branches; the object of the
invention being to attain a uniform operation of the signals, independent of the
character of the lines with which they are associated.
My correspondents give also as an improvement means to charge the storage
battery which forms the source of supply of the exchange while it is in use, or,
in other words, to supply the current directly from the dynamo, maintaining
the charged storage battery across the supply circuit for use at night and for
reserve in case of failure of the dynamo. The noise of the commutator of the
generator has until now prevented this practice, but I give herein two expedients
which are available. One of these consists in putting low resistance impedance
coils in the mains of the generator; the other and preferable method consists
in so subdividing the commutator and running the commutator at a high speed
that the number of pulsations from the commutator exceeds six or eight thousand
per second, at which point the noise from the commutator becomes inaudible.
In the design of an impedance coil which would be suitable for this purpose,
a bundle of annealed iron wires is employed, surrounded by a coil of wire; the
dimensions of the core and the size of the wire of the coil in each instance being
dependent upon the current requirements of the circuit in which it is used. A
device of this character has the property of smoothing out the ragged impulses,
caused by the charging dynamo, which, if allowed to remain, would develop
annoying disturbances in the telephone circuits.
In the construction of a special commutator for service in connection with the
current supply, there would be required a sufficient number of segments to
cause the current interruptions to exceed the audible period when the commu-
tator revolves at a safe speed. The design of such a commutator requires that
it be made of large diameter and that careful attention be devoted to anchoring
the segments in a secure manner. A commutator having about two hundred
segments revolved at a speed of thirty per second is found to produce the desired
result. No structural changes of the generator are required.
Figure 1 shows an improved scheme of circuits for receiving and transmitting
telephones in systems in which the transmitter is supplied from a central source
with current. The receiving telephone is placed in a shunt circuit around the
transmitting telephone whereby an increase of efficiency in transmitting tele-
phonic currents is attained through the removal of the impedance and resistance
of the receiving telephone from the line circuit.
Figure 1 represents two telephone lines, 1, 2, and 3, 4, which are assumed to
be connected in a telephone switchboard. In the switchboard, which is also a
point from which the lines receive their current supply for exciting the trans-
mitter, the line circuit is furnished with a bridge or cross conductor 5 which
includes a source a of current, together with windings band b₁ of impedance
coils for preventing the shunting of telephonic currents through the bridge.
The substation is equipped with a receiving telephone ca transmitting tele-
phone d, and induction coil e, having four windings and a condenser f.
The line circuit may be considered as being complete through winding e¹,
transmitting telephone 7, and winding e² of the induction coil. About the

page_text: transmitting telephone a shunt circuit C is arranged which includes serially a
winding of the induction coil, the receiving telephone c the condenser f and
the winding of the induction coil. The windings e¹ and e³ should of course
tend to magnetize the core in the same direction when traversed by current,
and windings and et should have similar relation to each other. Windings e¹
and should be so related to windings ee that they tend to magnetize the core
in the same direction as if they were traversed serially by a continuous current.
A steady current flows from battery a in the central office through both lines
to the substations thereof, finding circuit at each substation through the wind-
ing e transmitting telephone d and winding e² of the induction coil. An increase
in the resistance of the transmitting telephone d at a station tends to diminish
the currents through the windings e and e2 and for an instant diverts the cur-
rents through the shunt 6 which charges the condenser f; the current flowing
through windings and es is then in proper direction to induce an electro-
motive force in windings e and e² tending to still further diminish the current
there. A subsequent decrease in the resistance of transmitter d permits an
increased current to flow in the line circuit at the same time permitting the
discharge of condenser f; this discharge takes place through windings and e
in proper direction to accentuate the increased flow through windings el e
Sound waves striking the transmitter d therefore set up in the line circuit an
undulating current whose undulations are greatly amplified by the inductive.
action of the condenser f acting through the windings e³ and e. When the
receiving telephone e is of usual construction, the condenser f may be of two
microfarads capacity, under which conditions the impedance of the receiving
telephone appears to have no deleterious effect in the shunt circuit.
Undulations created in the line wire 1, 2, are not propagated through the
bridge 5, at the station of current supply, on account of the presence in the
bridge of the impedance coils bb¹, but traverse the line conductors 3 and 4
to the distant station. This current is substantially an rnating current,
which finds free circuit through the condenser f and the recg telephone c.
The efficience of the system in receiving telephonic curren... in no wise
impaired by placing the receiver c in the shunt circuit 6 instead the direct
line circuit, while the efficiency of transmission is greatly increased by eliminating
the impedance of the receiver from the line circuit; and the resistance of the
circuit to the exciting current is diminished.
Figure 2 illustrates two similar substations A and B which are assumed to
be connected together at a telephone switchboard, through a repeating coil
having four windings and a common source of current. Each substation com-
prises a high resistance bell a, a', permanently connected on the line in circuit
with a condenser g, g¹.
When the receiver h, h¹, is on the hook, the switch k, k, is not in connection
with the points m³, m², and the calling current from the central station flows
through the lines 1 and 2 through the bell a, a', actuating it, and through the
condenser g, g¹.
When the receiver is off the hook, the switch k, k', makes connection with the
two points m³. m², thereby connecting the transmitter d, d', through the primary
winding of the induction coil e, e¹ and by conductor 5 in bridge with the
lines 1 and 2; and at the same time closing the shunt circuit through the
secondary winding of the induction coil f¹, the conductor 6, the receiver h, h¹,
the condenser g, g¹, the transmitter d and the switch k, k¹.
Figure 3 shows the scheme of a practical mounting of a substation. Figure 4
shows how the substation may be changed to work with a local transmitter
battery without interfering with the other regular features of the common
battery system.
In the scheme shown in Figure 3, when the receiver is on the hook the primary
or the line circuit is from terminal L2 by conductor 5 to condenser a, thence
by conductors 6 and 7 to bell b through conductor 8 to earth.

page_text: When the receiver is off the hook the primary or line circuit is from ter-
minal L by conductor 13 to terminal 1, through the primary winding of the
induction coil to terminal 2, thence via conductor 14 to the contact point f,
which is now in connection with switch e, thence by conductor 11 to the trans-
mitter d and over conductor 12 to terminal L2. The shunt circuit is from ter-
minal L² over conductor 5 through condenser a over conductor 6 to terminal 3,
through the secondary winding of the induction coil to terminal 4 over con-
ductor 9, through the receiver c, over conductor 10, to contact f', which is now
connected to switch e, thence by conductor 11, through transmitter d and by
conductor 12 to L².
Terminals B and B are left spare and conductors 15 and 16 are not in use.
Figure 4 shows by dotted lines how the modifications for working with a
local transmitter battery may be made. The local transmitter battery is con-
nected between terminals B and B the induction coil is removed and a connec-
tion made between the terminals 1 and 4 and an ordinary transmitter with its
own induction coil is provided in place of the common battery transmitter.
The ringing circuit remains the same as described in connection with Figure 3.
When the receiver is off the hook the line circuit is from L' by conductor 13
to terminal 1, thence by conductor 13ª to terminal 4 then via conductor 9,
receiver c, conductor 10, contact f¹, switch e, conductor 11, through the secondary
winding of the induction coil and conductor 12 to terminal L2. The local cir-
cuit is from one pole of the transmitter battery to terminal B thence over con-
ductors 15 and 14 to contact f, switch e and conductor 11, through the primary
winding of the induction coil and transmitter d thence via conductor 16 to
the other pole of the local battery.
The present invention applies also to improvements in the circuits and opera-
tion of supervisory signals in connection with metallic circuits having permanent
ground branches, with metallic circuits free from such ground connections, and
with grounded circuits, indifferently. It consists in the combination with the
two conductors forming a plug circuit or link for uniting telephone lines, of a
source of current in a bridge of the plug circuit, an electro-magnet in each of
the link conductors and a signal controlled by these magnets jointly, the signal
being preferably concealed when both magnets are excited, and as respects the
use of these appliances with grounded lines, it further consists in a normal
partial return conductor, to excite one of the signal controlling magnets during
connection with the line.
The features of this improvement are shown diagrammatically in Figure 5.
This drawing represents the apparatus of three substations with a grounded
line extending from a central office to one of the stations, and a metallic circuit
party line extending from the same office to the remaining stations, together
with plugs and a plug circuit and other apparatus in accordance with this inven-
tion for uniting the lines and supervising the use of the circuit thus established
in the central office.
Each substation is furnished with transmitting and receiving telephones, a
call bell and a telephone switch for closing the line circuit through the tele-
phones during the use of these instruments. At the station of the grounded
line, the line conductor 1 is provided with two paths to the grounded return
conductor 2, one of which includes the polarized call bell a together with a
condenser a¹ and the other of which traverses the telephones 2 and 3 and is
controlled by the telephone switch. The rising of the switch, when relieved
of the weight of the receiving telephone, thus closes the line circuit as respects
continuous or unvarying current.
The apparatus at the station A' and A2 of the party line are of like character,
but are somewhat differently arranged in the circuit. At each station a bridge 3
of the line circuit 4, 5, exists controlled by the telephone switch a', which
includes the transmitting and receiving telephones; but at the station A¹ the
bell a is located in a ground branch 6 from the line conductor 5, no

page_text: condenser being interposed in this circuit, while at the station A2 the bell a is
similarly located in a ground branch 7 from the line conductor 4.
This arrange-
ment of the bells is to permit the selective operation of the bells at the different
stations; it being obviously possible to send a calling current over one line con-
ductor and the ground return to ring the bell at station A', over the line con-
ductor and the ground return to ring the bell at station A².
The line circuits of whatever nature are led to the line contacts of spring
jack 6 in a telephone switchboard, thence normal extensions are led through the
switch contacts of a cut off relay c to sources of current and individual or line
signals of special arrangement in accordance with the nature of the line.
Thus the extension of the line conductor 1 is led through the magnet winding
of a relay d to the pole of a battery e or other source of current.
It is cus-
tomary to provide also the wire 2 which forms within the switchboard the return
circuit for the line; this wire is connected with one contact piece of the spring-
jack and is then grounded, usually at a point outside of the switchboard. In
converting such a grounded line into a metallic circuit the portions of wire 2 at
the substations and at the central office are disconnected from earth and united
by an insulated wire, and the wire 2 is extended to the contact anvil of cut-off
relay c.
In carrying out this improvement however, I interpose a battery f of small
voltage in a grounded conductor 2 at the central office, for a purpose which will
be explained hereinafter. The relay d controls a local circuit 8 which includes a
secondary line signal, which may be a small incandescent lamp, placed near the
springjack of the line in the switchboard. The cut-off relay following the usual
practice is located in a conductor 9 grounded at one end and terminating in a
normally open contact ring b¹ of the springjack of the line.
The party line is similarly provided with a secondary line signal controlled by
the relay and is connected with a source of current c, but in this instance the
normal ground extension of line conductor 4 includes the magnet winding of the
relay, while the source of current e is interposed in the grounded extension of
the other line conductor 5. The purpose of this arrangement is to permit the
excitement of the relay only when a connection is completed between the line
conductors at one of the substations.
The apparatus for uniting the lines in the switchboard comprises plugs g and g¹
each with three contacts designed to register with the three contact parts of a
springjack, circuits uniting the line contacts of the plugs to form the plug circuit,
and other local conductors terminating in the local contacts of the plugs to bring
about the operation of certain appliances in the switch board. Thus the spherical
tips of the plugs are united by conductor 10 while the short rings constructed to
register with the longer springs of the springjacks, are united by a conductor 11.
The conductors 10 and 11 of the plug circuit traverse the windings of the repeat-
ing coil h, two serially connected windings of the coil being interposed in each
conductor; the points of junction of these windings are united by a bridge 12
of the plug circuit, which includes a source i of current. The pole of this source
of current adjacent to conductor 10 is grounded. The plug circuit traverses the
switch contacts of the usual calling keys k, k₁ and for looping a generator of
signalling current into circuit with plug g¹ to send calling current over either
or both of two line wires; it is connected with an operator's listening key
bringing a telephone into the plug circuit.
for
The sleeve contacts of the plugs, which register with the ring contacts of the
spring-jacks, form the terminals of conductors 13 and 14, respectively, which
lead to the free pole of a grounded battery m, and which include signals n and n¹.
The different signals n and n' refer to the corresponding plugs g and g¹, being
associated with them in the switchboard; their display is determined by the
application or withdrawal of shunts which are controlled by relays in the plug
circuit. The disposition of these relays in the plug circuit, and the arrangement
of circuits by which they control the supervisory signal lamps
n. and n', to pro-

page_text: duce a uniform operation of the signals when the plug circuits are used in
uniting lines of diverse types, constitute the essential features of this invention.
The controlling relays for the signal n are designated o and p; the former is
included in the portion of conductor 10 between the bridge 12 and the plug g,
and the latter in the like portion of conductor 11. The, relays and pl in
a like manner control the signal n¹ referring to the plug g', the former relay
being in the portion of conductor 10 leading from the bridge to the plug g', and
the latter relay being in a like part of conductor 11. The shunt through the
agency of which the relays o and 2 control the signal n consists in the wire 15
which traverses in series the switch contacts of the two relays o and p; this
wire may include a coil of low resistance, the diversion of the full current from
the signal lamp being unnecessary. A like shunt for the lamp n¹ exists in the
wire 16, whose continuity is controlled at two points by the relays o¹ and pl.
The act of calling for connection from a substation is the same in all stations;
it consists merely in taking the telephone from its switch for use. The mode in
which this act causes the display of the line or calling signal, however, varies in
the case of grounded lines and party lines. Thus the removal of a telephone
from its switch at the station A produces a closed circuit through the telephones
at that station which permits current to flow from battery e through the magnet
winding of relay d, over the line conductor 1 to the substation, and thence by
way of the return conductor 2 to earth, whereby the local circuit including the
secondary signal is closed and the signal lamp is lighted. In calling from a
station A or A2 the closure of the circuit through the telephones by the tele-
phone switch permits current to flow from the battery e of the party line through
the conductor 5, thence through the bridge including the telephones, returning
to the central office through conductor 4 of the line and traversing the magnet
winding of relay d. It will be noted that the battery has normally no circuit
through the relay, notwithstanding the existence of the permanent ground con-
nections with the line.
In response to the display of a line signal of any line, the attendant will insert
the plug into the springjack associated with the signal, and will bring her
telephone into connection with the plug circuit to learn from the calling sub-
scriber the order for the line with which connection is required. After receiving
the information she will insert the plug g' into the springjack of the line called
for, as that of the lines to station A¹ or A2; after which she will ring the bell
at the required station, by means of a key k if the line be a single station line,
or through the instrumentality of the proper key or if the line be a party
line, in accordance with well known methods.
The insertion of plug g into the spring jack b of any line closes a local circuit
made up of conductors 13, 9, in which current is thus permitted to flow from
batterm m to excite the supervisory lamp signal n and the cut-off relay C. The
cut-off relay severs the normal ground connections of the line and leaves the line
in closed circuit with the plug circuit; and through the medium of this circuit
with the line to the required station. The presence of plug g₁ in the spring jack
of the line called for similarly closes the local circuit 14, 9, of the line called for,
whereby the signal lamp n¹ is excited and the cut-off relay of the answering line
is energized and severs the ground connection of the latter line. The functions of
the parts thus far described are performed in this way in the case of any con-
nections, whether they be with grounded or metallic circuits, or with metallic
party lines. The behaviour of the relays op and o¹ pl is dependent on the nature
of the lines with which they become associated, however, and must be traced in
different cases.
When the calling line is, as has been described, a grounded line, the act of
answering a call brings the battery i into circuit with the line 1, 2, which is
closed at the station, whereby current is permitted to flow through the con-
ductor 11, traversing the winding of relay p, to the line wire 1, and thence to
grounded return conductor 2 at the substation; at the same time current is

page_text: U
produced by the battery in the grounded conductor 2 at the central office to the
conductor 10 of the plug circuit, and thus to earth through the magnet winding
of relay o. Magnet o is thus excited by the current which will remain constant
while the connection exists, while magnet ? becomes excited with a current
dependent on the position of the telephone switch at the calling station. Relay
closes the break in the shunt wire 15 which it controls, and maintains the con-
tinuity of this wire during the existence of the connection; magnet p similarly
closes the break which it controls while the telephone switch is in its alternate
position, the telephone being in use. The shunt wire is thus effective in divert-
ing current from the lamp n, so that this lamp remains dark while the telephone
at the calling station is in use, but becomes lighted whenever the telephone is
replaced on its switch.
Turning now to the operation of the relays o¹ and p¹: The insertion of plug g'
into the spring jack of the party line provides a circuit from battery i through
portions of conductors 10 and 11 of the plug circuit to the wires 5 and 4 of the
line circuit. Current will frow from conductors 11 and 4, through the ground
branch 7 at the substation including the bell, which will excite the relay p¹, and
will cause this relay to close the break which it controls in the shunt wire 16, but
no current will exist in the portion of conductor 10 which includes the winding
of relay o¹, since no source of current is found connected with the portions of the
plug circuit and line circuit which are directly connected with this instrument;
hence the shunt wire 16 will remain broken at the switch contacts of relay o¹, and
the lamp n', being not shunted, will remain lighted. Its illuminated condition
constitutes an indication to the operator that the subscriber at the station called
has as yet made no response. When the telephone is taken for use at either
station A¹ or A2 a bridge of the line circuit is closed at that point, as already
mentioned, so that a complete circuit is formed from battery i through a portion
of conductor 11, line wire 4, line wire 5, a portion of conductor 10, returning
thence to battery i; the current in this circuit excites the magnet of relay o¹
which closes the second break in the shunt 16, and thus brings about the
extinction of lamp . This signifies to the attendant a response to the call at
the station called.
It will be apparent that if the called line were a grounded circuit, the relays o'
and p would be operated in the way traced for the relays o and p in making con-
nection with the calling line. If the called line were a metallic circuit the
operation would be similar to this just described for the party line, the two relays
being excited by current passing out over one line wire, finding circuit through
the bridge closed in the telephones, and returning through the other line wire
to excite the second relay in the plug circuit. In general, each signal n and n¹
will be caused to indicate, by its lighted or dark condition, the position of the
switch at the station of any line with which it may be connected irrespective of
the nature of the line circuit.
Figure 6 illustrates another improvement. This figure represents two telephone
lines one a grounded special circuit and the other a metallic party line circuit
with grounds at different stations containing selective calling appliances, together
with signalling and switching apparatus for the lines in the switch-board, the
party line circuit being equipped with a device for maintaining the normal opera-
tion of the supervisory signals in accordance with the present invention.
All the substations of these lines are furnished with the usual receiving and
transmitting telephones a and a³, telephone switches a³ for closing bridges of
the line circuit through these instruments in the use of the telephones, and
polarized call bells a The bell at station is located in a bridge or ground
branch from the line together with a condenser at which interrupts the con-
tinuity of the line as to the battery currents made use of in signalling to the
office, while being complete as respects the alternating calling current for ringing
the bell. The single conductor 1 of this grounded circuit is led to the line con-
tacts of the spring jack 6 in the switch-board, from which it is prolonged through
the switch contacts of a cut-off relay c and through the magnet winding of a

page_text: signal-controlling relay d to one pole of a grounded battery e. The relay d
controls a secondary line signal d' associated with the springjack 6 in the switch-
board, through the agency of a normally broken local circuit 2, which it completes
when excited. The actuating magnet of the cut-off relay c is connected in a
local grounded conductor 3 which terminates in an insulated contact ring of the
springjack b.
At each of the stations A1 and A2 of the party line the bell a³ is connected in a
permanent ground branch from one of the line conductors--the bell at station A¹
being in a ground branch 4 from line conductor 5, and the bell at station A² being
in a ground branch 6 from line conductor 7. The line conductors lead, like that
of the grounded line, to the line contacts of a springjack b in the switch-board,
from which they are extended through the switch contacts of a cut-off relay c
to earth and to the pole of a grounded battery e, respectively; the magnet of
the signal-controlling relay d is, however, included in the extension of line con-
ductor 7, so that current reaches the magnet only when a bridge of the line
is closed through the telephone at one of the stations.
In the switch-board the usual pairs of connecting plugs f and fl are provided
for the use of the operator in uniting lines. Like line contacts of the plugs are
connected together through conductors 9 and 10 which constitute the plug circuit,
the usual calling keys g and g¹ being interposed in the conductors of the plug
circuit, and the listening key h being connected therewith for bringing the
telephone into a bridge of the plug circuit. It will be noted that one of the
calling keys g is adapted to apply one pole of a grounded source i of calling
current to one line conductor 7, to ring the bell a³ at station A2, while the other
key g is adapted to apply the same pole of the source of calling current to the
other line conductor 5 to ring the bell at station A'; the key g¹, however, when it
applied calling current to the line wire 5, also connected with the line wire 7 one
pole of a grounded battery k, for a purpose which will be hereinafter set forth.
The conductive continuity of the plug circuit 9, 10, is broken by interposing in
each conductor thereof two serially connected windings of a repeating coil 7, in a
well known way; the points of junction of the windings of these coils are led to
the poles of the battery k, which thus may serve for supplying. current to the
substation transmitters, if desired, as well as for operating supervising signals
associated with the plug circuit.
The conductor 10 of the plug circuit leading to each of the plugs traverses the
magnet winding of a supervisory relay, these being designated m and m¹,
respectively. Each of these magnets controls the display of a supervisory signal,
the signals being marked n and n¹, associated with the corresponding plug for fl.
The signal lamp n is included in a branch 11 from a grounded battery o to the
contact sleeve of plug f which is adapted to make connection with the test ring of
the spring jack b. Lamp n' is likewise included in a wire 12 leading from the
same battery to the corresponding part of plug f¹. The relays m and m¹ control
these signals n and n¹ through the agency of shunts 13 and 14, respectively,
which are completed when the relays are excited. These signals are of usual and
well known character in telephone exchanges. When a connection is established
between lines in the switch-board, it is intended that current shall flow from
battery through the conductors 9 and 10 of the plug circuit to each line, the
existence of the current being determined by the condition of the bridge including
the telephones at the substation of the line. A supervisory relay m or m² is in
the path of current to each of the lines; when the relay is excited by current
flowing in the line with which it is temporarily associated, it is designed to close
the shunt about the signal lamp, and thus to divert therefrom current flowing in
the local circuit completed in the act of making connection, to render the lamp
dark. Thus each supervisory signal lamp is to remain dark while the telephone
of the station with which it is in temporary association is in use, becoming lighted
when the bridge at the station is broken.
In providing for the uniform operation of these supervisory signals on rounded

page_text: metallic circuits like that leading to stations A1 and A2, I place in the line con-
ductor 7 of the line the magnet of a relay p. This magnet may be of moderate
resistance, and should preferably be shunted by a non-inductive resistance to
furnish a free path for telephone currents. This relay is responsive to currents
in the conductor 7, which, however, can occur only when a complete path is
established from line conductor 5 through a bridge at one of the stations A₁ or A2.
The switch contacts 2 22 of this relay control the continuity of a conductor 15
leading from the free pole of battery to the line conductor 5.
The
In order to trace the operation of the supervisory signals, and the control of the
signal associated with the party line through the agency of magnet p, let a
connection be assumed to originate at station A, to be extended to station A¹.
removal of the telephone from its switch at station A permits current to flow from
the batterye which excites the relay d and brings about the display of the line
signal in the switch-board. Answering the call, the operator inserts plug f
into the springjack b, at the same time bringing her telephone into the plug
circuit to learn the order. The insertion of the plug in the springjack completes
a local circuit of battery o through wires 11 and 3, wherein current excites the
cut-off relay c and causes this appliance to sever the normal ground connections
of the line. At the same time current is permitted to flow from battery k through
the portion of the plug circuit connected with the calling line, over the line
conductor, and through the telephones at the station to earth, whereby the
supervisory relay m is excited and closes the shunt about the supervisory lamp n.
Upon learning the subscriber's order, the operator inserts plug f¹ into spring-
jack of the line 5, 7, and depresses the key g' to ring the bell at the station A¹.
The insertion of plug f¹ in the springjack completes a local circuit 12, 3, which
includes the signal lamp n' and the magnet of cut-off relay c of the called line.
The cut-off relay severs the ground connections of the line in the exchange, and
the lamp n becomes lighted. The depression of the key gl connects one pole of
the source of alternating calling current with the line conductor 5, from
which the current finds circuit to station A¹ and through the ground branch 4 to
carth, ringing the bell at that station; it also applies one pole of battery k to
the line conductor 7, whereby a current is produced through relay 2, reaching
earth through the ground branch 6 at station A³, which excites the relay and
breaks the conductor 15 leading to earth from line wire 5 in the central office.
Having transmitted the specialized call to call the desired station, the operator
releases the key g¹. A circuit exists from battery k through a portion of con-
ductor 10 of the plug circuit including the supervisory relay m¹ to line wire 5 and
thence through the ground conductor 4 at station A¹, but as soon as the relay p
becomes inert a short circuit is formed from battery through wire 15 to the line
wire 5 in shunt of relay m², whereby the latter is deprived of current and caused to
maintain the break in the shunt about signal n¹. Hence the supervisory signal n
remains lighted to show that the called party had not responded. The taking of
the telephone at station A' in response to a call closes a bridge of the circuit
at that station, whereby current is permitted to flow over line wire 5, through the
bridge including the telephones at station A', returning through line wire 7
including the magnet of relay p, through a portion of conductor 9 of the plug
circuit, to earth in the central office. This current excites the relay p, which
breaks the short circuit 15 and diverts current through the relay m¹; this latter
appliance, becoming excited, closes the shunt about lamp n¹ and thus brings about
its extinction. The darkening of lamp n' is a signal to the operator that the
call to station A¹ has received attention.
It will be apparent that the replacement of the telephone upon the switch at
either station, by breaking the bridge closed through the telepone at the station,
will deprive the corresponding supervisory relay of current, and thus cause the
lighting of the corresponding lamp n or n¹; this result being attained directly in
the case of the grounded line, but indirectly through the agency of relay p, in

page_text: the case of the grounded metallic circuit line. The display of both signals may
be accepted by the attendant as a call for disconnection.
The nature of the controlling device will be dependent on the nature of the
line with which it is associated; both its character and the means by which
it controls the supervisory signal to compensate for the special nature of the line,
to bring the operation of the supervisory signals in connection with the line into
harmony with their operation in assocation with other lines, may be varied to a
considerable extent. In general, the last described improvement contemplates
broadly the provision of a device for each line of special nature which responds
to some predetermined act at a station of the special line, and which, in its
response, controls the supervisory signals to make them operate in the way usual
with lines of ordinary character.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I we declare that
what I claim is:-
1. The combination of a high resistance line and a source of supply current
in it with a high resistance transmitter at the substation capable of widely varying
its resistance under impact of sound waves.
2. The introduction of low resistance impedance coils in the mains to
the generator which must charge the storage battery or source of supply of the
exchange while it is in use.
3. Subdividing the commutator of the generator in such a way that the number
of pulsations from the commutator exceeds the number necessary to render the
noise from the commutator inaudible.
4. The combination with a telephone line and means connected therewith for
supplying current in the line, of a transmitting telephone in the line circuit, a
shunt about the transmitting telephone, and a receiving telephone and a con-
denser in the said shunt.
5. The combination with a telephone line and means for supplying current in
the line, of a transmitting telephone in the line circuit, and an induction coil
having one winding in the line circuit, a shunt of the transmitting telephone
including another winding of the induction coil, and a receiving telephone and a
condenser in the said shunt.
6. The combination with a telephone line and a source of current in a bridge
of the line, of a transmitting telephone in a bridge of the line at the substation,
an induction coil having two windings in the said bridge with the transmitting
telephone, a shunt circuit about the transmitting telephone, two windings of
the said induction coil in the said shunt and adjacent to the different terminals
of the transmitting telephone, respectively, and a receiving telephone and a
condenser in circuit with said shunt between the said windings in the shunt.
7. The combination with a metallic circuit telephone line and a switch at the
station thereof for completing the circuit of the line, a spring jack of the line,
and a plug and plug circuit for making connection with the springjack, of a
ground branch from each conductor of the plug circuit, and a source of current
in one of said branches, an electromagnet in the other of said branches, and a
supervisory signal controlled by the electromagnet, whereby the operation of
the signal is rendered independent of grounds on the telephone line.
8. The combination with a metallic circuit telephone line, of two line con-
ductors, a switch at the substation for uniting the line conductors, and ground
branches from the different conductors, a springjack of the line, and a plug and
plug circuit for making connection with the springjack of a ground branch from
each side of the plug circuit, a source of current in one of the branches, an electro-
magnet in the path of current through the other conductor of the plug circuit,
and a supervisory signal controlled by the magnet, substantially as described.
9. The combination with a telephone line and a switch at the station thereof

page_text: for changing the resistance of the line, of a source of current in a bridge of the
line in a central office, an electromagnet in the path of current from said source
to each line conductor, and a signal controlled by said magnets jointly, substan-
tially as described.
10. The combination with a telephone line having a switch at its station for
completing the line circuit in the use of the telephone, a springjack for the line,
a plug and plug circuit for making connection with the line through the agency
of the springjack, of a source of current in a bridge of the plug circuit, an electro-
magnet connected with each conductor of the plug circuit to be in the path of
current from said source to the corresponding line conductor, a signal or other
mechanism, and means for operating the said signal or mechanism through the
agency of either magnet; whereby the plug circuit may be operated when
associated with grounded lines, or metallic circuits, or grounded metallic circuits,
as described.
11. The combination with grounded circuit lines and grounded metallic circuit
lines, with switches at the stations thereof for changing the resistance of the
lines in the use of the telephones, springjacks for the lines, a plug and plug
circuit for making connection with any line by means of the springjack, of a
source of current in a bridge of the plug circuit, an electromagnet in the path
of current from said source to each line conductor of a line, switch contacts
controlled by each magnet, a supervisory signal, and a circuit thereof including
said switch contacts, made operative in the simultaneous actuation of the switch
contacts, as described.
12. The combination with grounded circuit lines and grounded metallic circuit
lines, each with a switch at its substation for closing the line circuit in the
use of the telephone, a springjack for each line, a plug and plug circuit for
making connection with the line by means of the springjack, of a bridge of
the plug circuit and a source of current therein, a relay having its winding in
each conductor of the plug circuit in a path of current from said source, a super-
visory signal in a local circuit, and a shunt of the signal controlled by the switch
contacts of both said relays, to be closed when both relays are excited, substantially
as described.
13. The combination with a wholly metallic circuit and partially metallic
circuit telephone lines, a switch at each station for closing the line circuit in
the use of the telephone, a springjack for each line, a plug and plug circuit for
making connection with any line by means of the springjack, of a bridge of
the plug circuit and a grounded source of current therein, an electromagnet
in each conductor of the plug circuit, a supervisory signal controlled by the said
electromagnets when simultaneously excited, and a source of current in the
grounded portion of each partially metallic line, substantially as described.
14. The combination with plugs and a plug circuit for uniting grounded circuits,
metallic circuits, and grounded metallic circuits in a switchboard, of a bridge of
the plug circuit and a source of current therein, an electromagnet in cach
conductor of the plug circuit between the said bridge and one of the plugs, and
a supervisory signal controlled jointly by the magnets adjacent to the same
plug, substantially as described.
15. The combination with telephone lines and switches at the stations thereof
for changing the resistance of the lines in the use of the telephones, spring-
jacks for the lines, a plug and plug circuit for making connection with any
line by means of the springjack, of a source of current connected with both
conductors of the plug circuit, an electro magnet in the path of current therefrom
to each conductor of the plug circuit, and a signal controlled jointly by said
magnets as described.
16. The combination with telephone lines, a supervisory signal and means for
temporarily associating it with any line, said lines being provided with different
instrumentalities at the stations thereof for operating the supervisory signal, of a
device in each line of one kind responsive to current of the same line for

page_text: operating the supervisory signal, and mechanism actuated thereby controlling
the supervisory signal to make it operate in the same way as when it is associated
with lines of different character, as described.
17. The combination with telephone lines provided at their substations with
different instrumentalities for operating supervising signals, said lines entering
a switch-board, link conductors in the switch-board for uniting any two lines,
and supervisory signals associated with the link conductors, said supervisory
signals being directly responsive to current for operating them in one class of
lines, and a device in each of the other class of lines responsive to the special
current therein for operating the supervisory signals, and intermediate mechanism
actuated thereby adapted to control the supervisory signal when associated with
the same line, whereby the operation of the supervisory signals from all sub-
stations is uniform, but is exercised through different agencies, as described.
18. The combination with grounded lines and grounded metallic circuits in
the same switch-board, and means at each substation for determining current in
the line in the use of the telephone, of a link conductor for uniting any two lines,
and a supervisory signal associated with the link conductor adapted to be brought
into direct connection with one of the line conductors to be responsive to current
therein, an electromagnet permanently connected with the other line conductor
of the metallic circuit line, and mechanism actuated by said magnet to control
the supervisory signal, whereby the action of the supervisory signal in connection
with grounded lines and grounded metallic lines is uniform, as described.
19. The combination with grounded circuit and grounded metallic circuit
telephone lines entering the same switch-board each line having a switch at its
substation for completing the circuit during the use of the telephone, of a link
conductor for uniting lines, a grounded source of current connected with said link
conductor, and supervisory signals in the path of current from said source of
current to the line conductors, a magnet permanently connected with the metallie
circuit line responsive to current therein determined in the completion of a
bridge of the line at the station thereof, and circuit connections of said magnet
adapted to be completed with the supervisory signal during connection, controlling
the operation of the supervisory signal associated with the line, whereby the
operation of the signals is made uniform, as described.
20. The combination with a metallic circuit telephone line with a permanent
ground from one conductor thereof, and a telephone switch at the station adapted
to close a bridge of the circuit in the use of the telephone, of a link conductor for
uniting lines adapted for connection with said grounded line conductor, a source
of current connected with the link conductor and a supervisory signal in the
path of current therefrom to the line, an electro-magnet permanently connected
with the other line conductor of said metallic circuit, and a short circuit of said
supervisory signal controlled by said electromagnet, as described.
21. The combination with a metallic circuit telephone line having a ground
branch from one line conductor and provided with a telephone switch for closing
a bridge of the circuit while the telephone is in use, of link conductors adapted
to form temporary extensions of said line conductor, each of said link conductors
being grounded, and a battery included in the ground branch from that conductor
which is directly connected to the grounded line conductor, a supervisory signal
in the path of current from said battery, an electromagnet permanently inter-
posed in the other line conductor, and a shunt of said signal controlled by said
magnet, as described.
22. The combination with a metallic circuit party telephone line with call
bells in ground branches from the different limbs thereof at different stations,
and with a telephone switch at each station for closing a bridge of the line in
the use of the telephone, link conductors for extending the line conductors
into connection with other lines, a ground branch from each of said link con-
ductors, a source of current in one of the ground branches, a supervisory signal in
the path of current therefrom to one of the line conductors, an electromagnet

page_text: permanently connected with the other line conductor, and a shunt of the super-
visory signal controlled by said magnet calling keys in the link conductors, one
for applying calling current to each of the line wires, and means controlled by
one of said keys to render said shunt inoperative while calling current is being
sent in the line conductor to which the shunt is applied as described.
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