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Патент USA US2404773

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July 30, 1946.
2,404,773
R. H‘- BROWN
APPARATUS FOR COMMUNICATION SYSTEMS
Filed Aug. 30, 1945
'
IN VENTOR.
. ?obem‘EBmwzz.
Hrs Arron/var.‘
Patented July 30, 1946
2,404,773
UNITED STATES PATENT OFFICE
2,404,773
APPARATUS FOR COMMUNICATION
SYSTEMS
Robert H. Brown, Westview, Pa., assignor to The
Union Switch & Signal Company, Swissvale,
Pa., a corporation of Pennsylvania
Application August 30, 1945, Serial No. 613,627
10 Claims. (Cl. 179-2)
1
2
My invention relates to apparatus for com
munication systems, and more particularly to
of my invention is the provision of novel and
calling apparatus for telephone systems.
improved calling apparatus for communication
systems.
A single pair of line wires is often used as a
Another feature of my invention is the provi
transmitting channel common to several differ
sion of improved voice operated calling apparatus
ent communication systems. For example, a two
for a telephone system.
wire line circuit along a railway may be used for
Again, a feature of my invention is the provi
a. dispatcher’s telephone circuit, a commercial
sion of calling apparatus of the type here in
telephone circuit, a telegraph circuit and a cen
volved incorporating novel time delay means
tralized tra?ic control circuit. In each such cir 10 which may readily be adjusted as to its delay
cuit, the current is of a characteristic individual
period, and which means requires that the calling
to the system and in the centralized trafiic con
current be continued during the full delay period
trol system, coded current of a time code type may
and if there is an interruption in the calling cur
be used. Thus, an operator at an oi?ce governs
rent, the full delay period is reestablished and
through the centralized traffic control circuit the lo the timing cycle must be restarted.
position of train signaling devices located at dif
Still another feature of my invention is the
ferent stations along the railway, current pulses
provision of calling apparatus of the type here
of a preselected code being used to select a de
contemplated incorporating novel means to pro
sired station and _a particular signaling device at
vide an answer back to the person calling.
the selected station. Also, in such centralized 20 Another feature of my invention is the provi
traf?c control systems coded current is transmit
sion of improved calling apparatus of high sensi
ted from the different stations to the cf?ce to in
tivity and which is readily adjustable as to its
dicate the positions of the signaling devices and
sensitivity.
the positions of trains in the vicinity of such sta
Other features, objects and advantages of my
tions.
In such a centralized traffic control systems
telephone communication is usually provided
' invention will appear as the speci?cation pro
gresses.
The foregoing objects, features and advantages
between each of the stations and the office, so
of my invention are accomplished through an
that a train crew member or a maintainer may
omce calling unit which incorporates a power
converse with the office operator in matters per 30 pack, a detecting means, a time delay means and
taining to train movements or the condition of
an answer back device.
the train signaling devices. In such telephone
The power pack is adaptable of converting en
facilities it is advantageous to have apparatus
ergy from a single alternating current source into
wherewith a person at any one of the stations can
direct current and alternating current of volt
call the o?ice operator. Such calling apparatus 35 ages suitable for tne different elements of the ap
cannot readily be of the common form for tel
ephone calling apparatus because of the inter
paratus.
The detecting means includes a receiving or
ference with the codes of the centralized traf?c
selector circuit, a ?rst electron tube and a ?rst
control system. Also, this calling means must
control relay. The selector circuit is coupled to
40
be free from interference with the currents used
the line circuit and is tuned to pass a preselect
by the other facilities of the line circuit. Again,
ed band of voice frequencies. The energy passed
the calling indicators effected by the calling
by this selector circuit is applied to a control
means must be of a distinctive character because
electrode of the ?rst electron tube which is pref
at such an o?lce there are usually several differ
erably of the controlled ionization type and the
ent indication bells and lights to indicate train " tube is tripped in response to such energy and
movements and other operating conditions.
when thus made conductive the ?rst control re
Furthermore, this calling means must be of rel
lay is energized by the conduction current. Thus
atively high sensitivity to provide reliable oper
this detecting means is responsive to energy of
ation through a relatively long line circuit and
because of wide variations of the voltage of the 50 the calling current frequency regardless of the
origin of such energy. A biasing voltage obtained
usual power source. At the same time the calling
from the power pack is applied to the ?rst elec
means must be free from operation by conver
tron tube and it is made adjustable and the call
sation and noise energy that appears on the line
ing can be set for high sensitivity. Also the sen
circuit.
'
In View of the foregoing conditions. a feature 55 sitivity of the calling unit can be adjusted in the
2,404,773
3
?eld to the condition of the particular line cir
cuit with which it is connected.
The time delay means includes a capacitor, 2.
second electron tub-e and a second control relay.
The capacitor is connected to the power pack
4
centralized tra?ic control system are not shown.
The type of centralized traffic control system is
immaterial and it may be any one of several of
the well known arrangements, The office of such
a system is indicated by a dot and dash rectangle
and is charged at a preselected direct voltage.
OF and one station of the system is indicated by
This capacitor is also connected to the second
a dot and dash rectangle ST, only the one station
being shown since the stations will have substan
tially duplicate facilities, and this one station is
prevents the tube from being normally tripped.
When the ?rst control relay is energized, this 10 sufficient to illustrate the invention.
The station ST is provided with a telephone
capacitor of the time delay means is disconnected
tube to provide that tube with a bias voltage that
from the power pack and is connected to a dis
charge circuit including a resistor and the capaci
tor is discharged at a predetermined rate. When
the discharge of the capacitor is carried far
enough the bias of the second tube is reduced to
a point where that tube is tripped and the second
control relay is energized by the conduction cun
rent of the tube. If for any reason the discharg
ing of the capacitor is interrupted it is quickly
recharged and the time cycle must be restarted.
This arrangement provides a selective control
against random noise and conversation of the
calling current frequency band operating the sec
ond relay, such noise energy and conversation
energy of this frequency band being ordinarily
of very short duration, so that the capacitor is
set which includes a transmitter 2 and a receiver
3 of the standard form and which set is connected
across the line wires through a connection which
preferably includes a blocking capacitor 4.
The of?ce GE‘ is provided with a telephone set
TS, a source of alternating current, a calling
unit indicated as a whole by a dotted rectangle
CU, calling indicators comprising a lamp 5 and
a bell 6, and a reset switch RS.
The office telephone set TS may be of any suit
able form and may comprise a standard hand
set or a loud speaker or a combination of these
devices.
The office source of alternating current having
terminals BX and CK may be of a usual com
mercial frequency and this source is connected
to terminals of the calling unit CU, terminal vBX
of the source being connected to terminal "I of
the second tube. The second electron tube is
provided with a stick feature by which the tube 30 the calling unit and terminal CX of the source
being connected to the two terminals 8 and 9 of
is retained conductive regardless of the charge
the unit, the connection to terminal 9 including
of the capacitor once the tube has been tripped.
a normally closed contact iii of reset switch RS,
The second control relay controls a call indi
as will be readily understood by an inspection
cator, such as a lamp, and this visual indicator
of the drawing.
once established remains in effect until the op
The calling unit CU includes a power pack
erator acknowledges the call by operating a reset
comprising a transformer Tl, a twin diode recti
switch. The second relay also governs a novel
?er tube RT, and two potentiometers, one in
circuit associated with the ?rst tube and through
cluding a resistor R3 and the other including
which novel circuit the first tube is transferred
two resistors R13 and R5 in series; a detecting
from the selector circuit to the time delay means
means comprising a transformer T2, a ?rst elec
and the ?rst tube is rendered conductive for a
tron tube Vi and a first control relay A; a time
predetermined time interval. A call bell is in
delay means comprising a capacitor Cl, a second
terposed in the anode circuit of the ?rst tube in
electron tube V2 and a second control relay B;
place of the ?rst control relay, and when the
and an answer back device AB.
?rst tube is tripped for this time interval the
The power pack of the unit CU is energized
call bell is rendered active as an audible ‘call in
from the of?ce source of alternating current and
dication.
>
provides ?lament voltage from the tubes and a
The second control relay when energized also
direct voltage suitable for the biasing of the tubes.
completes an energizing circuit for the answer
A primary Winding H of transformer TI is con
back device which is preferably of the buzzer
nected to terminals l and s, and a ?rst secondary
type, and this buzzer is operated ‘to supply to
winding E2 of the transformer is connected to
the line circuit an answer back current.
the filaments of the tubes as indicated conven
I shall describe one form of apparatus .em
tionally in the drawing, a mid'terminal of second
bodying my invention, and shall then point out
:1 Lu ary winding l2 being connected to ground elec
the novel features thereof in claims.
trode IS. A second secondary winding M of
The accompanying drawing is a diagrammatic
transformer Tl is connected across the anodes
view showing a form of apparatus embodying my
of the two sections of the twin diode tube RT,
invention when used in a centralized traffic vcon
and the cathodes of these two sections of the tube
trol system for railways.
are connected in multiple to one terminal of the
It is to be understood that the invention ‘is
potentiometer resistor R3 and to one terminal
not limited to a centralized traf?c control system
of the potentiometer resistors R4 and R5. The
in its use and this one use serves to illustrate the
other terminal of resistor R3 and the other ter
many places the apparatus is useful.
minal of resistors R18 and R5 are connected to a
Referring to the drawing, the reference char
mid terminal of the secondary winding M. Con
acters Y and Z designate line wires which extend
sequently a direct voltage is created across these
along a railway, and which are used as a circuit
potentiometers due to the recti?ed current, the
for different facilities, such as a dispatcher’s tele
not discharged for the required period to trip
value of such direct Voltage being predetermined
according to the proportioning of the parts. A
that the invention is not limited to a pair of line 70 by-pa-ss capacitor C2 is preferably connected
phone circuit, a telegraph circuit anda central
ized traffic control circuit. It is to be understood
across the potentiometer-s to by-pass the alter
hating current ripples of the recti?ed current.
The detecting means is provided with a receiv
communication only. In order not to complicate
ing or selector circuit which comprises the two
the drawing, these facilities except that of the
elephone communication associated with the 75 parts of a primary‘winding l5 of transformer T2
wires used in several different circuits and the
line wires Y and 2 may be used for telephone
2,404,773
5
connected in series through'a capacitor I6 and
which circuit is connected to terminals I1 and I8
of the unit CU and which terminals I‘! and I8 in
turn are connected across the line wires Y and Z
in multiple with the o?ice telephone set. This
selector circuit is tuned to pass a preselected band
of voice frequencies which, for illustration, may
contact 34 of relay A and back contact 3| of relay
B to the other terminal of the capacitor. Thus
capacitor CI is discharged at a rate predeter
mined by the value of the resistor R6 and the set
ting of the intermediate terminal 33. The inter
mediate terminal 31:!v is preferably mechanically
connected to a manually operable knob, not
be taken as being of the order of 1000 cycles per
second, but other voice frequencies can be used.
shown, mounted on the calling unit for adjust
I have found in practicing the invention that a 10
The electron tube V2 of the time delay means
may be any one of several well-known ‘types and
is shown as a hot cathode gas ?lled tetrode. Tube
calling band produced by having the person call
ing to whistle or blow into the telephone trans
mitter is satisfactory.
A secondary winding I9 of transformer T2 is
ment of the discharge rate of the capacitor CI.
V2 is provided with a connection to the capacitor
CI to bias the tube according to the charge of
connected to a control electrode of tube VI to 15 the capacitor. Normally, the positive plate of
capacitor CI is connected to cathode 35 of tube
control this tube in response to the energy passed
V2 through wire 40 and the negative plate of
by the selector circuit. To be explicit, a circuit
the capacitor is connected to control electrode
can be traced from the control electrode 20 of
36 of the tube through back contact 31 of relay
tube VI, through resistor 2I, back contact 22 of
B and resistor 38. Thus control electrode 35
control relay B, secondary winding I9, interme
is negative in potential with respect to the oath
diate terminal 23, of the potentiometer resistor
ode 35 by a voltage predetermined by the charge
R3, a portion of resistor R3 and wire 24 to cath
of capacitor CI. Tube V2 is provided with an
ode 25 of the tube VI. It is clear that the con
anode circuit receiving energy from the alternat
trol electrode 29 is provided with a bias voltage
ing current source, the circuit extending from
from the resistor R3, the control electrode being
terminal BX of the source through terminal ‘I
negative in potential with respect to the cathode
of the unit CU to a winding of relay B, anode
by a voltage predetermined by the setting of the
39 and tube space to cathode 35 of tube V2,
intermediate terminal 23. I preferably mechani
Wires 40, 24, 29 to terminal 9 of unit CU and
cally connect the intermediate terminal 23 to a
manual operable knob, not shown, mounted on 30 terminal II! of reset switch RS to terminal CX of
the alternating current source.
the calling unit for ready adjustment of the bias
The parts are proportioned for the voltage ap
voltage for the tube VI . This negative bias volt
plied to the anode of tube V2 to be ine?ective to
age for the tube VI is opposed by the positive half
trip the tube when the control electrode 36 is
cycles of the electromotive force induced in the
winding I9 due to the current passed by the se 35 biased by the voltage of capacitor CI, but when
capacitor CI is discharged to a preselected point
lector circuit.
'
the tube V2 is tripped and relay B is energized.
Tube VI may take any one of several types and
Relay B when energized to close front contact
is disclosed as a hot cathode gas ?lled tetrode.
4I completes a stick circuit connection between
Tube VI is provided with an anode circuit receiv
ing energy from the alternating current source, 40 control electrode 36 and cathode 35 and the tube
retained conductive due to control electrode 36
the terminal BX of the source being connected
and cathode 35 being at substantially the same
through terminal ‘I of the unit to a winding of
potential. That is to say, the tube V2 is re
the control relay A and thence through resistor
tained conductive until such time as the anode
25, back contact 21 of relay B, anode 28 and tube
circuit is opened due to the operation of the reset
space to cathode 2-5 of tube VI, wires 24 and 29,
switch RS in a manner to appear later.
terminal 9 of the unit CU, and contact II) of the
With relay B picked up to close front contact
reset switch RS to the other terminal CX of the
42 the call indicator 5 is energized by current
alternating current source. The parts are so pro
flowing from the top terminal of the secondary
portioned that the bias negative voltage applied
to control electrode 20 from resistor R3 prevents 50 winding I2 of transformer TI through wire 45,
front contact 42 of relay B, terminal 46 of the
the anode voltage from tripping tube VI but a
unit CU, lamp 5, and ground electrodes 41 and
relatively small voltage of secondary winding I9
I3 to the mid terminal of secondary winding I2.
That is to say, the call indicator lamp 5 is illumi
nated as long as the control relay B is energized.
Relay B on picking up to close front contacts
43 and 48 completes circuits by which tube VI is
the relay energized during the negative half cycles
disconnected from the receiving or selector cir
of the alternating current when the tube is non
cuit and is connected to the'capacitor CI andby
conductive.
Capacitor CI of the time delay means is con 60 which the relay A is disconnected and bell 6 is
interposed in the anode circuit of tube VI. Since
nected across resistor R4 through a charging cir
relay B is not energized until the capacitor CI
cuit which can be traced from the top terminal of
is substantially discharged, the bias voltage ap
resistor R4 as viewed in the drawing, through
plied from capacitor CI to control electrode 20
capacitor CI, back contact 3| of relay B and back
contact 32 of relay A to the junction terminal of 65 of tube VI through the connection including
front contact 48 of relay B is low and tube VI
resistors R4 and R5, and the capacitor CI is
is tripped and anode current ?ows through the
charged at a direct voltage equal to the voltage
bell 6 from terminal BX of the current source
drop across resistor R4, When relay A is picked
to terminal 49 of unit CU and thence through
up in response to the tripping of the electron tube
V I of the detecting means, the condenser CI is 70 resistor 50, front contact 43 of relay B, anode
28 and tube space to cathode 25, wires 24 and
disconnected from the charging circuit and is
29, terminal 9 and contact IQ of switch RS to
connected to a discharging circuit and which dis
terminal OK. The bell 6 is thus sounded as an
charging circuit can be traced from the top termi
audible call indicator while tube VI is retained
nal of capacitor CI through a portion of resistor
R6, an adjustable intermediate terminal 33, front 75 conductive by this circuit. Relay A when deen
to oppose the bias voltage causes the tube to be
tripped and relay A to be energized by the cur—
rent passed by the tube. A capacitor 30 is con
nected across the winding of relay A to retain
2,404,773
8
ergized to ‘close back contact 32 completes the
charging circuit for vcapacitor CI, the charge be
the call hell 6 rings for a preselected ‘period of
say two seconds.
The picking up of control relay B also ener
gizes the answer back device AB and the device
charging circuit due to relay B picking up to Cl AB is operated to supply current to the line cir
ing built up on the capacitor at a predetermined
rate because resistor R2 is now included in the
open back contact 3|. After a preselected time
interval of say 2 seconds, the charge on capacitor
CI builds up to a voltage su?icient to prevent
tube VI from tripping during the positive half
cycles of the alternating current and tube VI is
deionized and thebell? ‘stops ringing.
The picking up of relay B to close front con
tact 44 completes a circuit from the answer back
device AB, which device is energized and oper
ated to ‘supply a current to the line circuit.
The device AB may be of ‘any one of several
different forms, ‘and is shown as a buzzer ener
gized by alternating current from secondary
winding 52 of transformer TI, the circuit ex
tending from the top terminal of secondary wind- 1
ing I2, through wire 45, front contact 44 of relay
B, secondary winding ii ‘of transformer T2,
winding of the buzzer AB, back contact 52 of the
buzzer, and ground electrodes 53 and, I3 to the
mid terminal of secondary winding I2. With the
buzzer thus energized, current is transferred from
winding 5I of transformer T2 to winding I5 and
from winding I5 current is applied to the line
wires for operating the telephone receiver at the
station ST.
The parts are so proportioned that .
this answer back current thus applied to the line
circuit would produce a distinctive tone in the
telephone receiver at the station ST.
In describing the operation ‘of the apparatus
I shall assume that ‘power is applied to the unit
CU and no energy is received from the line cir~
cuit. Under this normal condition, the tubes VI
and V2 are biased to a non-conductive condition
by voltages supplied from the power pack and re
lays A and B are d‘eenergized so that the call
indicators 5 and I3 are inactive.
Assuming that a person at station ST wishes
to telephone to the o?lce operator, the telephone
set at the station is removed from the hook and
the calling person either whistles or blows, as
prearranged, into the transmitter at the station.
This action creates a calling current of a pre
selected frequency band, and which calling cur
rent is applied to terminals I? and I8 of the o?ice
calling unit and is passed by the selector circuit. .\
The resultant electromotive force induced in sec
ondary winding I9 is supplied to the control elec
trode 257 of tube VI to drive the control electrode
in the positive direction with the result that the
tube is tripped causing the control relay A to be
energized. Relay A on picking up transfers ca
pacitor CI of the time delay means to its dis
charge circuit and the direct voltage across the
capacitor is discharged at a rate predetermined
by the setting of the intermediate terminal 33 of 60
the resistor R6 as described h'ereinbefore.
Assuming the person calling continues his call
for a preselected interval, the discharge of ca
pacitor CI is carried to a point where the bias
of tube V2 is reduced in voltage to a point that
permits the tube V2 to trip and the control relay
B is energized. With control relay 3 energized
to close front contact 4|, tube V2 is sealed in
by its stick feature and remains conductive re
gardless of the charge on the capacitor Cl. The
calling lamp 5 is now illuminated due to the clos
ing of ‘front contact 42 of relay B and becomes
a calling indication.
Relay B on picking up to
close front contact 43 and 48 brings the transfer
circuits associated with tube VI into play and
cuit to produce a tone in the telephone receiver
at station ST, so that the person calling knows
that his call has been properly received at the
office.
The office operator in acknowledging this call
will take his telephone set to initiate communi
cation with the calling person at the station ST.
The operator also will operate the reset switch
RS which opens the anode circuit for tubes VI
and V2 and the calling unit is restored to its
normal condition ready to receive another call.
Assuming that energy of the calling current
frequency appears in the line circuit due to some
noise condition or due to a particular syllable
or word in ‘the conversation, such energy is passed
by the selector circuit, the tube VI is tripped,
and the control relay A is picked up. This noise
energy will ordinarily be of short duration and
consequently the tube VI is deionized and relay
A released before the capacitor CI is discharged
to a point where the tube V2 is tripped. With
relay A thus released, capacitor ‘CI is reconnected
to its charging circuit and the charge on the
capacitor is immediately restored and the full
delay period of the device becomes reestablished.
Thus, a call will not be made effective due to a
succession of pulses of noise energy occurring
in short intervals apart.
Apparatus here disclosed has the advantages
that it is adjustable for relatively high sensi
tivity and a call can be accomplished through
a relatively long line circuit. A relatively large
variation in the voltage of the source of power
does not greatly Vary the sensitivity of the unit
or the established delay period. The sensitivity
and the delay period of the device can both be
‘quickly adjusted to suit the operating conditions
of the line circuit with ‘which the apparatus is
associated. Successive pulses of current of the
calling frequency due to noise energy or due to
the conversation will not ordinarily establish a
call because of the delay period of the device.
Although ‘I have herein shown and described
but one form of apparatus for communication
systems embodying ‘my invention, it is understood
that various changes and modifications may be
made therein within the scope of the appended
claims without departing from ‘the spirit and
scope of my invention.
Having thus described my invention, what I
claim is:
1. In apparatus for communication systems,
the combination ‘comprising, supply means to
transmit a calling current, a selector circuit
adapted to receive such calling current, a con
trolled ionization tube provided with an anode
cathode circuit including a power source and an
‘electromagnet and with a control electrode cath
ode circuit including a capacitor, a charging cir
cuit including a source of direct voltage, a dis
charging circuit including a resistor, circuit means
governed by said selector circuit and operable to
connect either said charging circuit or said dis
charging circuit across said capacitor according
as calling current is not or is being received, said
charging circuit to charge the capacitor at a
voltage as required to bias said control electrode
negative in potential with respect to said cathode
to retain the tube deionized, said discharging cir
Icuit to discharge said capacitor at a preselected
2,404,77 8
'
rate to permit said tube to be ionized and said
electromagnet energized in a preselected time in
terval, and a call indicator governed by said
electromagnet.
2. In apparatus for communication systems, the
combination comprising, means operable at times
10
of said relay to indicate the reception of such
calling current,'and a manually operable reset
switch to open said anode cathode circuit to de
ionize the tube.
'5. In apparatus for communication systems,
the combination comprising, an oii‘ice and a sta
to transmit a calling current of a given charac
tion connected by a line circuit, station telephone
teristic, a receiving circuit adapted to receive such
means to supply at times to said line circuit a
calling current, a controlled ionization tube pro
calling current having a given voice frequency
vided with an anode cathode circuit including a 10 band, an o?ice receiving circuit connected to said
power source and a relay and with a control elec
line circuit and tuned to pass said frequency band,
trode cathode circuit including a capacitor, a
charging circuit including a source of direct volt
age, a discharging circuit including impedance,
a circuit element operatively associated with said
an o?ice gas ?lled tube provided with an anode
circuit including a power source and a relay and
with a control electrode circuit including a
capacitor, o?ice means operatively associated with
said receiving circuit to connect a source of
circuit or said discharging circuit to said capac
direct voltage or a resistor across said capacitor
itor according as said calling current is not or is
according as said calling current is not or is re
being received, said charging circuit to charge
ceived, said direct voltage source to charge said
said capacitor to bias said tube as required to 20 capacitor to bias the tube as required to retain the
retain the tube non-conductive, said discharging
tube deionized, said resistor to discharge the
circuit to discharge the capacitor to reduce
capacitor‘ as required to trip the tube and ener
the bias of the tube for the tube to be tripped
gize said relay in a predetermined time interval,
and said relay energized in a predetermined time
an indication circuit including a front contact of
interval, and a call indication circuit including a 25 said relay and an indicator to indicate reception
front contact of said relay.
of the calling current, an of?ce vibrator coupled
3. In apparatus for communication systems, the
to said line circuit, and an operating circuit in
combination comprising, means to supply at times
cluding a front contact of said relay to energize
a calling current of a given frequency band, a
said vibrator to supply an answer back current to
selector circuit tuned to receive current of said 30 said station telephone means.
frequency band, a controlled ionization tube, said
6. In apparatus for communication systems, the
tube having an anode cathode circuit including
combination comprising, calling means operable
a power source and a relay, a control electrode
to supply at times a calling current, a selector
cathode circuit including a capacitor for said
circuit to receive such calling current, a ?rst con
tube, a charging circuit including a direct Voltage
trolled ionization tube provided with an anode
source having connections to said capacitor, a
circuit including a power source and a ?rst relay
discharging circuit including a resistor having
and with a control electrode circuit including an
connections to said capacitor, said charging cir
element coupled to said selector circuit, said anode
cuit eii‘ective to charge the capacitor as required
and control electrode circuits to ionize said ?rst
to bias the tube to a non-conductive condition, 40 tube and energize said ?rst relay in response to
said discharging circuit e?ective to discharge the
reception of said calling current, a second con
capacitor as required to trip the tube and ener
trolled ionization tube provided with an anode
receiving circuit to connect either said charging
gize said relay in a preselected time interval,
means governed by said selector circuit to close
either the connections of the charging circuit or
of the discharging circuit according as calling
current is not or is being received whereby said
relay is energized only when the calling current
continues for said preselected time interval, and
a call indication means governed by said relay '
and made active only when the relay is energized.
4. In apparatus for communication systems,
the combination comprising, means to supply at
times a calling current of a given frequency band,
circuit including a power source and a second
relay and with a control electrode circuit includ
ing a biasing means, said biasing means effective
to retain said second tube deionized, means in
cluding a front contact of said first relay con
nected to said biasing means to vary its effect at
a preselected rate to ionize said second tube and
energize said second relay in a predetermined
time interval whereby said second relay is ener
gized only when the calling current continues
uninterrupted for said time interval, and a call
indicator governed by said second relay.
a receiving circuit tuned to receive current of said 55
7. In apparatus for communication systems,
frequency band, a controlled ionization tube, said
the combination comprising, transmitting means
tube having an anode cathode circuit including a
power source and a relay, a control electrode
cathode circuit including a capacitor for said tube,
a charging circuit including a direct voltage
source having connections to said capacitor, a
discharging circuit including a resistor having
connections to said capacitor, said charging cir
cuit effective to charge the capacitor as required
to bias the tube to a non-conductive condition,
said discharging circuit effective to discharge the
capacitor as required to trip the tube and ener
gize said relay in a preselected time interval,
means governed by said receiving circuit to close
to transmit from a station to an of?ce a calling
current of a preselected voice frequency band, a
selector circuit at said o?ice tuned to pass said
frequency band and arranged to receive said call
ing current, a first c-?ice gas tube having an anode
circuit including a power source and a ?rst relay
and a control electrode circuit including a wind
_ ing coupled to said selector circuit, said ?rst gas
tube normally non-conductive and tripped in re
sponse to said calling current to energize said
?rst relay, a second o?ice gas tube having an
anode circuit including a power source and a sec
ond relay and a control electrode circuit includ
either the connections of the charging circuit or 70 ing a capacitor, means including a back contact
of the discharging circuit according as calling
of said ?rst relay to charge said capacitor at a
current is not or is being received, means includ
direct voltage and said capacitor poled to render
ing a front contact of said relay to connect said
said second tube control electrode negative in po
control electrode to said cathode to retain the
tential with respect to the tube cathode to re
tube conductive, means including a front contact
tain the tube non-conductive, means including a
11
12
front contact of said ?rst relay to connect a re
sistor across said capacitor to discharge the ca—
pacitor to a voltage where, said second tube is
tripped in a predetermined time interval to ener
gize said second relay, and a call indication cir
cuit including a front contact of said second relay.
quired to retain said second tube non-conductive,
a discharging circuit including a front, contact
of said ?rst relay and a resistor connected to said
capacitor to discharge said capacitor at a rate
as required to trip said second tube and energize
said. second relay in a predetermined time inter
val, a call. bell, means including contacts of said
second relay to disconnect said ?rst relay and
8. In apparatus for communication systems,
the combination comprising, transmitting means
connect the call bell, in the anode circuit of said
?rst tube, means including a contact of said sec
ond relay to interpose a resistor in said charging
to transmit from a station to an oi?ce a calling
current of a preselected voice frequency band, a
receiving circuit at said o?ice tuned to pass said
frequency band and arranged to receive said call
ing current, a ?rst o-f?ce gas tube having an an
ode circuit including a power source and a ?rst
relay and a control electrode circuit including a
~ of said second relay to switch said capacitor to the
winding coupled to said receiving circuit, said ?rst
gas tube normally non-conductive and tripped in
response to said calling current, to energize said
control electrode circuit of the ?rst tube to trip
thev ?rst tube and operate said call bell for said
preselected time period, when said second relay is
circuit to delay the charging of the capacitor for
a preselected time period when the second
relay is energized, and means including contacts
energized.
?rst relay, a second of?ce gas tube having an
anode circuit including a power source and a sec
20
10. In combination, a ?rst and a second. gas
tube,‘ a ?rst and a second relay, a call bell, said
ond relay and a control electrode circuit including
?rst tube provided with an anode circuit having
a capacitor, means including a back contact of
two paths one of which paths includes a current
said ?rst relay to charge said capacitor at a. di
source, said ?rst relay and a back contact of said
rect voltage and. said capacitor poled to render
second relay; and the other of Which paths in
said second tube control electrode negative in‘ po
cludes said current source, said call bell and a
tential with respect to the tube cathode to retain
front contact of said second relay; said second
the tube non-conductive, means including a front
tube provided with an anode circuit including a.
contact of said ?rst relay to connect a resistor
current source and said second relay, said ?rst
across said capacitor to discharge the capacitor
to a voltage where said second tube is tripped in 30 tube provided with a control electrode circuit
having two paths one of which paths includes a
a predetermined time interval to energize said
back contact of said second relay, a winding and
second relay, means including a front contact of
a bias voltage source; and the other of which
said second relay to connect said second tube con
paths includes a front contact of said second
trol electrode to the cathode. of the tube to retain
the tube conductive, and a call indicator lamp 35 relay and a capacitor; said second tube provided
with a control electrode circuit including said ca
controlled through, a front contact of said second
pacitor, a charging circuit including a back con
relay.
tact. of said ?rst relay and a voltage source con
9. In apparatus for communication. systems,
the combination comprising, transmitting means
nected to said capacitor to charge the capacitor
to transmit, from a station to an o?ice a calling 40 to create a bias voltage for said second tube to
current of a preselected voice frequency band, a
receiving circuit at said of?ce tuned to pass said
retain the tube non-conductive, a discharging
frequency band and arranged to receive. said
calling current, a'?rst of?ce gas tube having an
lay and a resistor connected to saidv capacitor to
discharge the capacitor at a given rate to trip
said second tube in a predetermined time interval,
anode circuit including a power source and a ?rst
relay and a control electrode. circuit including a
Winding coupled to said receiving circuit, said
?rst gas tube normally non-conductive and
tripped in response to said calling current to, ener
gize said ?rst relay, a second o?ice gas tube hav
ing an, anode circuit including a power source and
a second relay and a control electrode circuit
including a capacitor, a charging circuit includ
ing a back contact of said ?rst relay and a direct
voltage source to charge said capacitor as re 55
circuit including a front contact of said ?rst re
means including a contact of said second relay
to interpose a resistor in said charging circuit
when the second relay is energized to charge the
capacitor in a preselected time period, and supply
means to at times induce in said winding an elec
tromotive force to trip said ?rst tube whereby
said call bell is. sounded for said preselected time
period when said electromotive force continues
for said predetermined time interval.
ROBERT. E. BROWN.
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