close

Вход

Забыли?

вход по аккаунту

?

Патент USA US2117358

код для вставки
May i7, 1938.
W. P. PLACE
2,117,358
COMMUNICATION SYSTEM
>F'iled Feb. 6, 1934
Toßeopz'vinÜ/:M
Appapal‘us
T0 Tpanfmz'z‘z‘mg
Appapafar
SM' _55K-TAT Fülle!" ¿4M
f
1
15
`
INVENTOR
Willard RPZCZC@`
BY @X1/JNM
> _ HIS
ATTQRNEY
2,117,358
Patented May 17, 1938
UNITED STATES PATENT OFFICE
2,117,358
COMMUNICATION SYSTEM
Willard P. Place, Wilkinsburg, Pa., assigner to
The Union Switch & Signal Company, Swiss
vale, Pa., a corporation of Pennsylvania
Application February 6, 1934, Serial No. '709,971
7 Claims. (Cl. Z50-6)
My invention relates to communication sys
tems, and particularly to ycarrier telephone sys
tems using suppressed carrier transmission. `
An object of my invention is the provision, in
5 systems of the type referred to, of an improved
circuit arrangement in conjunction With anv elec
tron tube modulator-oscillator for suppression of
the carrier which is modulated b-y the voice fre
quencies. Another object of my invention is`the
provision of a similar circuit arrangement in con
junction with an electron tube oscillator for sup
pression of the reintroduced carrier which is
_mixed with the incoming sideband for demodu
lation. Other objects and advantages of my _in
vention will appear as the speciñcation progresses.
In carrier telephone systems using suppressed
carrier transmission heretofore proposed, the
combination resulting from modulation of the
carrier by voice frequencies is applied to a selec'
tive network of balanced circuits and the car
20 rier and one sideband are substantially sup
pressed and the remaining sideband is passed t0
the communication circuit. The carrier being of
irelatively large magnitude, its suppression is
`,more difñcult and necessitates a relatively elab
orate ñlter arrangement. A balanced modulator
oscillator consisting of two Vacuum tubes operat
ing in the conventional push-pull manner has
also been proposed for carrier telephone systems
for balancing out the carrier but such arrange
ment requires two Vacuum tubes. In my present
invention a bridge type circuit arrangement for
an electron tube functioning in conjunction with
a tuned circuit for generating a carrier current
which is to be modulated by voice frequencies
is provided. This bridge circuit substantially
eliminates the carrier from the output of the
tube by confining the carrier to the bridge circuit,
and the associated filter needs only to select
between the upper and the lower sideb-and fre
,40 quencies produced from modulation with the re
viewof one form of apparatus embodying my in
vention, and which apparatus is particularly
adapted for telephone communication between
two locations on a railway train. The apparatus
of Fig. 1 is that for transmitting, and the appa 5
ratus of Fig. 2 is that for receiving. It will be
understood that in practicing my invention both
locations will be equipped with the transmitting
apparatus of Fig. 1 and the receiving apparatus
of Fig. 2 so that two-way operation may be ac
complished.
Fig. 3 is a diagram illustrating the i
bridge type circuit arrangement of Figs. 1 and 2.
Although the apparatus of Figs. 1 and 2 may
be located at any two points: on a railway train,
they will be referred to in the following descrip
tion as being mounted on the locomotive and
in the Caboose of a freight train, respectively. As
stated above, in actual practice, both the locomo
tive and the Caboose will be equipped with ‘the
apparatus of Figs. 1 and 2 in order to provide for
two-way communication.
The communication
circuit from one end of the train to the `other
may take different forms, and preferably isthat
disclosed in the L. O. Grondahl application for
Letters Patent of the United States Serial No.
450,135, ñled May 6, 1930, for Electric train sig
naling systems, and wherewith transmission is
accomplished between the two ends of a `train
throughthe medium of the traffic rails.
Although `a specific adaptation of my inven 30
tion is here disclosed, it will be understood that
I do not wish to limit myself to telephone systems
for railway trains, and my invention is equally
useful to other telephone systems of the type
here involved. The form here disclosed will serve, 35
however, to illustrate the many applications of
my invention.
As will appear hereinafter, my
invention is not limited to telephone communica
tion and may be utilized for the transmission of
code messages or for the transmission of control
impulses.
sult that the iilter network can be of compara
Referring to Fig. 1, the reference character
‘
tively simple construction. At the receiving lo
MO designates apparatus for generating carrier
cation a similar bridge type circuit for the tuned
circuit and the electron tube which generate the
carrier to be mixed with the incoming sideband
for demodulation is provided. This last men
current of any convenient frequency say, for ex
tioned bridge circuit operates to substantially
ceiving apparatus by coniining the carrier to the
cuit associated therewith by a bridge type circuit
arrangement. The electron tube 5 may take
different forms and preferably is a pentode hav
bridge circuit.
ing a filament 6, a plate l, a screen grid 8 and a `
eliminate the reintroduced carrier from the re
'
I will describe one form of apparatus embody
ing my invention, and will then point out the
novel features thereof in claims.
In the accompanying drawing, Figs. 1 and 2,
when taken together constitute a diagrammatic
ample, '2’000 `cycles per second and which is to be
modulated by voice frequencies. The apparatus ‘
MO comprises an electron tube and a tuned cir
control grid 9. The ñlament 6 is heated by a
battery l0 in the customary manner and is pro
vided with a cathode grid ll interposed between
the screen grid 8 and the plate 1 to shield the
55
2
2,117,358
screen grid from the secondary electron emission
from the plate. A tuned circuit I9 consisting of
an inductor I2 and a condenser I5 is associated
with the tube 5 by having one terminal, the right
hand terminal as shown in Fig. 1, connected with
the plate 'I over a wire I6 and its opposite or left
hand terminal connected with the screen grid 8
over a wire I 1. A suitable source of current here
shown as a battery I3 is connected between a
mid terminal I8 of the inductor I2 and the ñla
ment 6, the primary winding I4 of a transformer
TI being interposed between the mid terminal I8
and the battery I3.
The parts are so propor
tioned that substantially an equal voltage is ap
15 plied to the plate ‘I and the screen grid 8. The
tube 5 is preferably of the pentode type which
functions properly with equal voltage applied to
the plate and screen grid, such tubes being well
known to the art. The parts are further so pro
20 portioned that oscillations take place between the
plate l and the screen grid 8 through the tuned
circuit I9 which oscillations, as stated above, are
of a frequency of '7000 cycles per second. It will
be understood, of course, that other frequencies
25 could be generated and that the frequency of '7000
cycles per second is assumed by way of illustra
tion only. It is clear that there is current flowing
between the plate 'i and the filament 6 and a
similar current iiowing between the screen grid
30 8 and the ñlament 8, tube 5 being preferably of
such characteristics that the alternating current
components of these currents are of approximate
ly equal magnitude in response to approximately
equal voltages impressed upon the plate and
35 screen grid. It will be understood, however, that
pentode tubes having characteristics other 'than
that which produces a substantially equal ñow
of current as the result of equal voltage on the
plate and screen grid may be employed if found
40 desirable, the mid terminal I 8 of the inductor
I2 being so adjusted as to produce a balanced
condition. These conductances of the tube 5
may be represented by resistors Rp and Rg con~
nected between the filament 6 and plate 1, and
45 between the filament S and grid 8, respectively.
To visualize these internal impedances of the tube
5, the ñctitious resistors Rp and Rg are shown
on the drawing by dotted lines. However, since
the internal impedances of the tube 5 will ordi
50 narily vary somewhat with voltage and different
individual tubes, actual resistors Rp and Rg may
be connected in the circuits at the locations shown
if found desirable to do so in order to obtain
greater stability.
It is at once apparent that this arrangement
between the tube 5 and the tuned circuit Iii forms
a bridge circuit, the portions of the inductor I2
»n either side of the mid terminal I8 forming
two arms of the bridge, and the plate and grid
60 resistors Rp and Rg forming the other two arms
of the bridge. In Fig. 3 this bridge circuit is
shown diagrammatically that it may be more
clearly understood. When oscillations are gen
erated between the plate and the screen grid, the
65 only part of the carrier current flowing in the
connection from the mid terminal I8 to the fila
ment 6 is a small part that may be caused by an
55
unbalanced condition of the bridge circuit.
This carrier frequency current is modulated by
70 voice frequencies in the following manner. The
control grid 9 of the tube 5 is provided with a
circuit including the secondary winding 20 of a
transformer T2 and a battery 2|. The primary
winding 22 of the transformer T2 is included in
a circuit which also contains a battery 23 and a
telephone transmitter or microphone M. Hence,
vibrations produced by sound impulses in the
microphone M cause corresponding variations in
the current flowing in the primary winding 22
which variations induce an electromotive force
of a corresponding frequency in the secondary
winding 20 and this electromotive force, in turn,
is impressed between the control grid 9 and the
filament 6 of the tube 5. With. the instantaneous
potential of the control grid B with respect to the
filament E varied at the relatively low voice fre 10
quencies produced by sound impulses in the mi
crophone M, the amplitude in the oscillations tak
ing place in the tuned circuit I9 is varied accord
ingly. It follows, therefore, that the carrier fre 15
quency is modulated in accordance with the voice
frequencies and, consequently, upper and lower
sideband frequencies are produced.
Since most of the carrier is confined to the
bridge circuit, and since the voice frequencies are 20
not aiïected by the bridge circuit, the current
flowing through the primary winding I 4 of the
transformer TI chiefly consists of voice frequen
cies and the upper and the lower sideband fre
quencies. It follows that the electromotive force
induced in the secondary winding 24 of the trans
former TI chiefly consists of the sideband fre
quencies and Voice frequencies, only the small
unbalanced portion of the carrier being carried
over.
This electromotive force induced in the 30
secondary winding 24 is conveyed to a band-pass
filter BPF so proportioned and adjusted as to
pass one sideband with very little attenuation
and to substantially suppress all other frequen
cies, the upper sideband being preferably passed. 35
The filter BPF may take different forms sev
eral of which are well-known to the art and as
its specific structure forms no part of my inven
tion, it is shown conventionally only in order
to simplify the drawing. It is clear from the 40
foregoing description, however, that the magni
tude of the current applied to the band-pass
filter BPF will be relatively small, the major por
tion of the carrier being eliminated by the bridge
circuit, and hence this filter may be relatively 45
simple in construction.
The upper sideband frequency passed by the
filter BPF is supplied to the communication cir
cuit, in this instance being ñrst ampliñed to a
relatively high energy level. As here shown, the 50
sideband passed by the ñlter BPF is impressed be
tween the grid 25 and the filament 26 of an elec
tron tube amplifier 2l with the result that the
upper sideband frequencies are reproduced in the
plate circuit of the tube 21 greatly increased in 55
amplitude. The plate circuit for the tube 2l in
cludes the input side of an amplifier transmitter
AT shown conventionally only and preferably con
sisting of two electron tubes connected to operate
in the well-known push-pull manner, and, hence 60
the upper sideband frequencies are further am
pliñed to a relatively high energy level. The out
put side of the amplifier transmitter AT includes
the primary winding 28 of an output transformer
T3, the secondary winding 29 of which is adapted
65
to be coupled with the communication circuit
through the medium of a pair of inductor coils 3U
and 3|.
The inductor coils 3U and 3l are mounted on
the locomotive in inductive relation with the traf
ñc rails I and Ia, respectively. Normally these 70
inductoi‘ coils will be connected with the receiv
ing apparatus on the locomotive to be described
later over normally closed contacts 5I and 52 of
acircuit controlling selector SW. Reversing this
75
3
2,117,358
Ul
circuit controlling selector SW to the position in
dicated by the dotted lines in Fig. 1, transfers
the coils 30 and 3| from the receiving apparatus
to the secondary winding 29 of the output trans
former T3, the circuit being completed over the
contacts 56 and 5l. In the form here shown the
circuit controlling selector SW is manually oper
ated. It will be understood, however, that the
selector SW may be automatically operated by
suitable coding apparatus and the coils 30 and 3!
alternately connected with the receiving and
transmitting apparatus should it seem desirable
to do so.
Referring to Fig.`2, 33 and 34 are inductor coils
mounted on the caboose in inductive relation with
the traffic rails l and la, respectively. These coils
30 and 3i are connected with an input filter Fl
over normally closed contacts 35 and 36 of a
manually operated circuit controlling switch SWI .
20 The filter FI is preferably a band-pass filter, the
parts of which are so proportioned and adjusted
as to pass a band of frequencies. having a width
substantially equal to the voice frequency range
and to attenuate all other frequencies. In this
25 instance the filter Fl is so proportioned as to pass
the upper sideband of the carrier of the appara
tus of Fig. 1 modulated by the voice frequencies.
That is, the filter Fl passes a band extending from
7500 to 9500 cycles, the carrier having been as
30 sumed to be I7000 cycles per second and the voice
frequencies being taken as extending from 500
to 2500 cycles. This upper sideband passed by
the ñlter Fl is applied to the input of an ampli
fier AM and is made to appear in the output cir
35 cuit of that amplifier greatly increased in am
plitude. The iilter Fl and amplifier AM may each
be any one of several well-known types for such
devices and as the specific type of each forms
no part of my present invention, they are shown
40 conventionally only for the sake of simplicity.
The output of the amplifier AM includes the pri
mary winding 3l of a coupling transformer T4
and hence an electromotive force having a fre
quency corresponding to the sideband picked up
45 from the traiiic rails is induced in the secondary
winding 38 of that transformer.
.
The receiving apparatus. of Fig. 2 is provide
with a demodulator D which includes a pentode
45 and an associated tuned circuit 49 both pref
50 erably similar to corresponding devices of the
modulator oscillator MO of Fig. l. The bridge
circuit arrangement by which the tuned circuit
49 of Fig. 2 is connected with the plate 41 and
screen grid 48 of the pentode 45 is identical to
5.5 that described for the tuned circuit I9 and pen
tode 5 of Fig. l and it is thought not necessary to
repeat the description. Suffice it to say that the
parts are so proportioned and adjusted that oscil
lations of the carrier frequency of '7000 cycles per
60 second are generated and ñow in the bridge cir
cuit, the small unbalanced portion of the car
rier only flowing in the primary winding 44 of a
transformer T5 interposed between the mid ter
minal 50 of the inductor 42 and the battery 43.
It is clear that this carrier will be mixed with
the sideband frequencies induced in the secondary
Winding 33 of the coupling transformer T4 and
applied to the control grid 49, and that there
will be produced corresponding upper and lower
sidebands. The lower sideband will consist of
the received upper sideband less r1000 cycles, name
1y, a band ranging from 500 to 2500 cycles, it
being recalled that the upper sideband consists
of '7500 to 9500 cycles. In other words, this lower
75 sideband will correspond to voice frequencies.
The upper sideband resulting from the mixing
of the local carrier with the received upper side
band frequencies will consist of the received
sideband plus 7000 cycles. The combination pro
duced by the mixing of the local carrier with the
received sideband will appear in the primary
winding 44 of the transformer T5 and will induce
an electromotive force of corresponding fre
quencies in the secondary winding 53 of that
transformer. The secondary winding 53 is con 10
nected with the input side of a band-pass ñlter
F3 having parts so proportioned and adjusted as
to pass the voice frequencies and to substantially
suppress the remaining products of demodulation.
The voice frequencies passed by the filter F3 are 15
then applied to a telephone receiver here shown
as a loud-speaker LS, after having been first am
pliñed
whose
ing 54
ing 55
by an ampliñer AMI of the usual type and
output circuit includes the primary wind
of a transformer T6, the secondary wind 20
of which is connected with the operating
winding of the loud-speaker LS.
To describe the operation of my system as a
whole I shall assume that the circuit controlling
switches SW and SW! occupy the position illus 25
trated on the drawing with the result that the
receiving apparatus on the locomotive and the
caboose are both coupled with the communication
circuit. As stated hereinbefore, both locations
will be provided with the transmitting apparatus 30
and the receiving apparatus of Figs. 1 and 2, re
spectively. To telephone from the locomotive to
the caboose the operator on the locomotive will
reverse the circuit controlling switch SW and
speak into the microphone M. The upper side 35
band is then supplied to the traiiic rails through
the medium of the inductor coils 30 and 3l hav
ing ñrst been amplified, however, to a relatively
high energy level. The transmitted upper side
band frequencies will be picked up from the traffic 40
rails at the caboose by the inductor coils 33 and
34 and impressed upon the filter FI since the»
switch SW is now in the position for connecting
the coils 33 and 34 to they receiving apparatus.
After amplification the received sideband fre 4.5
quencies are demodulated and the resulting voice
frequencies are supplied to the caboose loud
speaker. To permit conversation from the
caboose to the locomotive the caboose operator
will shift the circuit controlling switch SWI to 50
the position for connecting the inductor coils 33
and 30.! with the transmitting apparatus on the
caboose and the locomotive operator will restore
the circuit controller SW to the position illus
trated for connecting the receiving apparatus on 55
the locomotive with the inductor coils 30 and 3|.
From this point on the operation will be similar to
that already described in telephoning from the
locomotive to the caboose.
While a telephone system has been described, it
is clear that by replacing the microphone M with
a generator adapted io supply a predetermined
frequency within the voice frequency range, say
for example, a frequency of 1000 cycles per sec
ond, and then coding this current according to a
prearranged code, the loud-speaker at the other
location will sound a note corresponding to the
prearranged code and code messages can be com
municated between the two locations. Further
inore, by replacing the loud-speaker LS with
tuned circuit networks selectively responsive to
different low frequencies within the voice fre
quency range, an automatic control can be estab
lished between the two locations
Although I have herein shown and `described 75
4
2,117,358
only one form of apparatus embodying my in
vention, it is understood that various changes and
modiñcations 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:
l. In combination; an electron tube provided
with a cathode, a plate and two grids; a tuned
10 circuit having opposite terminals connected one
directly to said plate and the other directly to one
terminal and cathode, means to connect the out
put side of said first ñlter between the other grid
and cathode of the tube, a transformer having
one winding interposed in the connection between
said mid-terminal and the cathode anda second
winding connected across the input terminals of
said second filter, and means for at times con
necting the input terminals of the ñrst ñlter with
a communication circuit.
4. In combination, a communication circuit, a l0
ñlter adapted to pass a given side band of a carrier
of said grids and said circuit including an in
ductor, circuit means for connecting a mid-ter
minal of said inductor with said cathode, a cur
15 rent source disposed in said circuit means to
of predetermined frequency modulated with a
signaling frequency, means to connect at times
the input terminals of said ñlter with said cir
supply substantially equal voltages to said plate
plate and two grids; a tuned circuit including an
and said one grid for causing oscillations of a
inductor and a condenser and tuned to resonance
predetermined carrier frequency to be generated
by the tuned circuit and balanced out of said
20 circuit means, means for varying the potential
of the other grid of the tube with respect to the
cathode at a given frequency for modulating said
oscillations whei‘eby side bands corresponding to
said cai‘ricr modulated at said given frequency
25 flow in said circuit means with the carrier fre~
quency substantially eliminated, and means cou
pled with said circuit means for receiving said
side bands.
2. In combination; an electron tube provided
30 with two grids as well as a plate and a cathode,
a tuned circuit having opposite terminals con
nected one directly to said plate and the other
directly to one of said grids and said circuit in
cluding an inductor, a circuit connection for
l35 connecting a mid-terminal of said inductor with
the cathode to form a bridge circuit consisting >of
the two portions of said inductor and the tube
impedances existing between the plate and the
cathode and between said one grid and the cath
40 ode, a source of current interposed in said circuit
connection to supply'voltages to the plate and
said one grid for causing oscillations of a pre
determined carrier frequency between the plate
and said one grid through the tuned circuit and
45 which are balanced out by said bridge circuit,
means for impressing between the other grid and
the cathode a side band telephone current whereby
side band frequencies resulting from demodula
tion ñow in said circuit connection with the car
50
rier frequency substantially eliminated, receiving
apparatus including a loud~speaker and a filter
adapted to pass voice `frequencies, and a trans
former having one winding interposed in said
circuit connection and a second winding con
55 nected with the input terminals of the filter of the
receiving apparatus.
3. In combination with telephone receiving ap
paratus including a ñrst filter adapted to pass a
given side band of a predetermined carrier fre
60 quency modulated with voice frequencies, a sec
ond filter adapted to pass voice frequencies and
a loud-speaker connected with the output side of
said second filter; an electron tube having two
grids as well as a plate and a cathode, a tuned
65 circuit including an inductor and a condenser
and tuned to resonance at said predetermined
carrier frequency, means to connect one terminal
of said tuned circuit directly to the plate and a
second terminal of said circuit directly to one of
70 the grids of said tube, means including a source
of current for connecting a mid-terminal of said
inductor with the cathode of said tube for causing
the tuned circuit to produce oscillations of said
carrier frequency and for suppressing said carrier
75 frequency in the connection between said mid
cuit; an electron tube provided with a cathode, a 15
at said predetermined carrier frequency, means to
connect one terminal of said tuned circuit directly
to said plate and a second terminal directly to one 20
of said grids, other means including asource of cur
rent for connecting a mid-terminal of said induc
tor with said cathode for causing said tunedcircuit
to produce oscillations of said carrier frequency
and for suppressing said carrier frequency in the 25
connection between said mid-terminal and cath
ode, a transformer having one winding interposed
in the connection between said mid-terminal and
cathode, receiving means including a signaling
device responsive to said signaling frequency and 30
a filter adapted to pass such frequency and conà
nected to a second winding of said transformer,
and means to connect the output terminals of the
ñrst mentioned filter with the other grid and
cathode of said tube.
35
5. In combination; an electron tube provided
with a cathode, a plate and two grids; a tuned
circuit having one terminal connected directly to
said plate and a second terminal connected di
rectly to one of said grids and including an in
ductor, circuit means for connecting a mid-ter
minal of said inductor with said cathode to form
a bridge circuit consisting of the two portions of
said inductor and the tube impedances existingbe
tween said plate and the cathode and between
said one grid and the cathode, a source of current 45
interposed in said circuit means to supply sub
stantially equal direct current voltages to said
plate and said one grid for causing oscillations
to take place between the plate and said one '
grid through the tuned circuit, and means for 50
impressing upon the other grid of the tube the
frequencies of a signaling current to vary the am
plitude of said oscillations as a function of the
instantaneous value of the signaling current to
cause current of the resultant side band frequen 55
cies with the carrier suppressed to flow between
said mid-terminal and said cathode.
6. In combination; an electron tube provided
with a cathode, a plate and two grids; a tuned
circuit having its opposite terminals connected 60
one directly to the plate and the other directly to
one of said grids and including an inductor, cir
cuit means for connecting a mid-terminal of said
inductor with said cathode, a current source dis~
posed in said circuit means to supply voltage to 65
said plate and said one grid for causing the tuned
circuit to generate a predetermined carrier fre
quency current, means for varying the potential
of the other grid of the tube with respect to the
cathode at the frequency of a signaling current 70
to vary the amplitude of the carrier current as
a function of the instantaneous value of the
signaling current to produce in said circuit means
the resultant side band frequencies with the car
75
2,117,358
rier frequency eliminated, and means coupled With
said circuit means for receiving said side bands.
'7. In combination; an electron tube provided
With a cathode, a plate and two grids; a tuned
circuit having its opposite terminals connected
one directly to said plate and the other directly
to one of said grids and including an inductor,
circuit means for connecting a mid-terminal of
said inductor with the cathode to form a bridge
circuit consisting of the two portions of said in
ductor and the tube impedances existing between
the plate and the cathode and between said one
grid and the cathode, a source of current inter
posed in said circuit means to supply voltage to
5
the plate and said one grid for causing oscilla
tions of a predetermined carrier frequency be
tween the plate and said one grid through the
tuned circuit, means for varying the potential
of the other grid of the tube with respect to the
cathode at a given frequency to vary the ampli
tude of said oscillations as a function of the in
stantaneous value of said given frequency to pro
duce in said circuit means the resultant side band
frequencies with the carrier frequency substan 10
tially eliminated, and means coupled with said
circuit means for receiving said side bands.
WILLARD P. PLACE.
Документ
Категория
Без категории
Просмотров
0
Размер файла
842 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа