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Патент USA US2137123

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Nov. 1-5, 1938.
H. M. LEWIS ET AL.
2,137,123
TELEVISION SYSTEM
Filed Oct. 4, 1935
3 Sheets-Sheet l
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INVENTORS
AROLD M. LEWIS,
ISON CA EIN.
ATTORN EY
NOV. 15, 1938-
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TELEVISION SYSTEM
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INVENTORS
HAROLD ‘M. LEWIS,
BY MZDISON
ATTORNEY
Patented Nov. 15, 1938
2,137,123
5 PTENT
I 2,137,123
TELEVISION SYSTEM
Harold M. Lewis, Douglaston, Long Island, and
Madison Cawein, Manhasset, N. Y., assignors
to Hazeltine Corporation, a‘corporatlon of Del
aware
Application October 4, 1935, Serial No. 43,548
11 Claims. (Cl. 178-75)
‘ This invention relates to television systems for
lumination may be controlled by adjusting the
the reception and utilization of vision- and
potential applied to one or more of the control
sound-modulated carrier waves, and particularly electrodes, as for instance the control grid, or
to methods of, and apparatus for, automatically" ‘~- screen, to vary the intensity of the cathode ray.
5 controlling such systems to provide improved op
When such an adjustment is made to the ex 5
eration and insure faithful image and sound re
tent that the cathode ray does not reach the end
production.
of the tube with su?icient intensity to illuminate
The invention is especially directed to the au . the screen, it may be termed a fade-out adjust
tomatic control of the background illumination ment or control and hereinafter the term “fade
10 of the fluorescent screen of a cathode-ray tube out control” will be employed to express this op
eration.
in a system such as above described, and is fur
ther directed to the automatic control, in co
In certain proposed television systems, alter
operation with such background illumination nate carriers are provided with vision modula
control, of the contrast of the picture detail in
15 the reproduced image, as well as the reproduc
tion and sound modulation, respectively, for the
transmission of both the scene and the sound of ll
a single program by adjacent carriers. In the
tion of sound, in such system.
According to the present practice in television
reception, picture signals or video-frequencies
design for receiving apparatus for such systems,
corresponding in amplitude to varying values of
the prevention of undesirable effects caused by
light and shade in the subject of transmission
the presence of the sound-modulated waves in 20
are applied to the control grid of a cathode-ray
tube to vary the intensity of the cathode ray or
beam to reproduce the picture detail. For the
purpose of scanning the ?uorescent screen of the
25 tube, saw-tooth'current or voltage waves are gen
erated in the receiver and are applied so as to
produce electrostatic or magnetic ?elds of saw
tooth form, to direct the ray horizontally and
vertically and thereby trace the well-known rec
30 tilinear scanning pattern on the screen.
In or
der to synchronize the horizontal or line-scan
ning action and the vertical or picture-scanning
action at the receiver with the corresponding ac
tions at the transmitter, the television carrier is
35 modulated by synchronizing impulses at the end
of each line period and each picture or frame
period, and these impulses are utilized to con
trol or operate the scanning wave generators.
In the arrangements of the prior art, it has or
40 dinarily been necessary for these generators to
be continuously operative, since without their
operation the cathode ray would remain focused
on a single spot on the screen, with resultant
damage to the tube or, in any event, an intense
45 spot of light on- the screen which would be ob
jectionable to the eye.
A preferred type of modulation for television
carrier waves is “negative modulation”, that is,
special problems are presented with regard to
the television channel of the receiver and by the
presence of vision-modulated waves in the sound
channel of the receiver, during tuning.
It will thus be apparent that television recep
tion may be substantially improved by the pro
25
vision of an automatic control of the cathode
ray, whereby the ray will be present with suf
?cient intensity to illuminate the screen only at
such times as a signal of proper type and of suf
ficient amplitude for reproducing an intelligible 30
image is being received and proper scanning ac
tion is being provided. An arrangement pro
viding such a control may be aptly termed an
“automatic fade-out control" and may be re
ferred to simply as “A. F. C.”
35
Ideal operating conditions may be more closely
approached by the provision, in cooperation with
an automatic fade-out control, of automatic con
trol of the contrast of the picture detail in ac
cordance with the amplitude of the received car
rier. Such “automatic contrast control” may be
referred to simply as “A. C. C.”
Finally, it will also be apparent that, in sys
tems where alternate carriers have sound and
40
vision modulations, respectively, materially im 45
ceeding the amplitude necessary to present com
proved reception may be obtained by the pro
vision, in cooperation with the automatic fade
out control and the automatic contrast control,
of an automatic control of the reproduction of
sound, whereby the receiver will be silenced 0
when video-frequencies are present in the sound
channel of the receiver, as for instance, during a
tuning operation when the sound channel is tuned
plete black on the screen.
to a vision-modulated carrier.
modulation whereby increases in carrier ampli
0 tude represent decreases in illumination and syn
chronizing impulse peaks appear as points of
maximum amplitude of the carrier wave ex
55
10
In a cathode-ray system the background il
It is, therefore, a primary object of this in
2
2,187,193
vention to provide an improved method of, and ' vlated signal is tuned in under conditions such ‘
means for, automatically controlling the back
that the screen is scanned under synchronized
ground illumination in a cathode-ray system in
accordance with the characteristics of received
CR
vision-modulated carrier waves and ‘with the
scanning action of the receiver.
-
A further object is to provide a method of,
and means for, automatically controlling the
contrast of the detail of the reproduced image, in
10 cooperation with the above-mentioned type of
background illumination control or, automatic
fade-out control.
A still further object is to provide a method of,
and means for, automatically controlling the re
15 production of sound in a receiver designed for the
reception of alternate carriers modulated by
sound and vision frequencies, respectively, to pre
vent undesirable effects of vision-modulation fre
quencies in the sound channel of the receiver.
20
For a better understanding of our invention, to
gether with other and further objects thereof,
reference is had to the following description,
taken in connection with the accompanying draw
ings, and its scope will be pointed out in the ap
25 pended claims.
In accordance with the present invention, the
control of the background illumination, or auto
matic fade-out control, is accomplished by ap
plying a bias voltage to one of the control elec
30
trodes of the cathode-ray system, which voltage
is derived by recti?cation of a modulation com
ponent unique to a vision-modulated carrier,
or-by recti?cation of a part of the locally gen
erated scanning impulses controlled by such car
Preferably, such control electrode of the
35 rier.
cathode-ray system is normally maintained at
such a potential that the electron ray is of in
sui?cient intensity to illuminate the screen, and
the automatic fade-out control voltage is applied
40 positively to effect illumination of the screen only
when the received carrier is of a predetermined
amplitude or characteristic to e?'ect proper scan~
ning.
The recti?er for producing the automatic fade
45 out control voltages may be a separate device, or
a single recti?er may be employed to produce both
the modulation components of the carrier and
unidirectional voltage for the automatic fade-out
control.
Further, the recti?er which derives the auto
matic fade-out control voltage may be connected
at various points in the system. Thus, in a pre
ferred embodiment of the invention, the auto
matic fade-out control recti?er is connected to
the output of, or to an appropriate .point in, the
55 line-frequency generator circuit and is thus de
pendent thereon, so that without proper scanning
action there can be no background illumination;
in other embodiments, this recti?er is connected
60 to the output of the carrier-frequency ampli?er
or to the output of the video-frequency ampli?er.
The systems for producing the automatic fade
out control voltages are made selective, either by
virtue of the point in the receiver at which the
65 automatic fade-out control recti?er is connected,
as in the ?rst-mentioned embodiment; by the
provision of selective circuits in connection there
with; or by virtue of the type of recti?cation em
ployed, as for instance, peak detection of the
synchronizing impulses of the received carrier, to
50
the end that no beam will be present unless a
proper signal is being received and/or proper
scanning is being effected.
Thus, according to the present invention the
75 screen is illuminated only when a vision-modu
control, whereby a picture is reproduced; or, in
other-words, only signals representing image in
telligence may be shown. When a vision-modu
lated carrier is “tuned in”, the picture appears,
with proper scanning, and when the carrier is
"tuned out”, the scanning ceases and the picture
fades out. Injuries or' undesirable effects which
would be occasioned by the stopping of the ray
at a spot on the screen are completely obviated
and, inasmuch as the screen is darkened in ab
sence of a proper signal, the necessity heretofore
present of providing continuously operating scan
ning generators in order to prevent such injuries
and undesirable effects is avoided.
Automatic contrast control is preferably pro
vided in cooperation with the automatic fade-out
control by applying to the grids of the carrier
frequency ampli?er tubes negative biasing po
tentials variable in accordance with the intensity
of the received carrier, in a manner similar to the
automatic ampli?cation control of sound broad
cast receivers. The automatic contrast control
voltage may be derived from the same recti?er 25
that produces the automatic fade-out control
voltages or from a separate rectifier and from the
same or different points in the system, as desired.
Also, in a system of the type described, designed
for alternate sound and vision carriers, the repro 30
duction of sound is preferably controlled so as to
prevent video-frequencies from being reproduced
by the sound channel of the receiver,_as’ would
otherwise result when the sound channel is tuned
through a vision-modulated carrier, This may be 35
accomplished by applying a voltage from the
audo-frequency channel to a selecting, amplifying
and rectifying arrangement to derive therefrom a >
negative biasing voltage only if and when video
frequencies are present in the sound channel of
the receiver. This biasing voltage may be applied
to the control grids of the audio-frequency ampli
?er tubes, or other suitable tubes, to silence the
sound reproducer.
In the accompanying drawings, Fig. 1 is a cir
cuit diagram, partly schematic, of a. complete 45
television receiving system embodying the present
invention and including both vision~ and sound
modulated carrier receiving and reproducing
channels; Fig. 2a is a graph of the modulation
voltage derived by detecting a self-synchronizing
type of “negatively modulated” carrier- wave; Fig.
2b is a graph of the unidirectional voltage de
rived by peak detection of the detected wave
shown in Fig. 2a; while Figs. 3, 4 and 5 are circuit
diagrams, also partly schematic, of modi?ed
55
forms of the television system of Fig. 1 in which
the several automatic control bias voltages are
derived from di?erent points of the system and/ or
by means of common or independent recti?ers.
Referring now particularly to Fig. 1 of the 60
drawings, the system there illustrated comprises
a receiver of the superheterodyne type including
an antenna and ground system lll—l I, connect
ed to a radio-frequency ampli?er 12, which is
connected in cascade with an oscillator-modula
tor I 3, an intermediate-frequency ampli?er H, a '
65
detector IS, a video-frequency ampli?er l6 and
a cathode-ray tube l1, constituting the vision
frequency channel of the receiver. The ele 70
ments or components Ill-J6 may all be of con
ventional well-known construction so that de-
tailed illustration and description thereof is
deemed unnecessary herein.
The cathode-ray tube l1 comprises the usual 75
3
2,187,123
envelope 18 containing, in the order named, a
quency carrier which, in systems where alternate
cathode heater IS‘, a cathode 20, a main or video
control grid 2|, a screen 22, a ?rst anode 23, a
second anode 24, and the usual ?uorescent screen
25 at the end of the tube. Line-frequency elec
trostatic de?ecting or scanning plates 26 are dis
of the order of one or more megacycles from the
sound-modulated intermediate-frequency car
carriers are modulated, respectively, by vision‘
frequencies and sound frequencies, will be spaced
rier, to which the ampli?er 33 is tuned. The
selected frequencies are ampli?ed in the‘ampli
?ers i4. and 33 and supplied therefrom to the
coils 21 are disposed at opposite sides of the tube detectors l5 and 34, respectively.
The detector 34 produces the audio frequencies 10
10 for de?ecting the beam in a direction normal to
the direction of de?ection effected by the plates of'modulation of the sound carrier and supplies _
26. The output of the video-frequency ampli?er them to the audio-frequency ampli?er 35 where
is connected to the control grid 2| by way of the by they are ampli?ed and supplied inthe usual
coupling condenser 28 and isolating resistance manner to the loudspeaker 36 for reproduction.
It should be here noted that the detector ii of 15
15 29 for controlling the intensity of the cathode
ray in accordance with the video-frequencies, as the television channel is designed to develop in
its output and deliver to the ampli?er l6 video
in usual practice.
For developing saw-tooth voltage waves for frequencies corresponding to the envelope of av
the plates 26 and saw-tooth current waves for vision-modulated carrier, particularly a self
20 the coils 21, to effect scanning action by the cath- . synchronizing, negatively modulated carrier, for
ode ray, a line-frequency generator 30 and‘ a the reception of which the receiver of this inven
picture-frequency generator 3| are provided. tion is especially applicable.‘ The video-fre
The‘ output of the video-frequency ampli?er I6 quency output or envelope of such a negatively
is connected to these generators for controlling modulated carrier is graphically shown in Fig.
or operating them in proper synchronism with 2a. Here, the impulse peaks‘for synchronizing 25
the line- and picture-frequency generators are
the scanning at the transmitter. The genera
posed within the envelope l8, and picture-fre
quency electromagnetic de?ecting git/scanning
tors may be of any well-known or suitable de
sign, such as, for instance, that described in
copending application, Serial No. 5,781, ?led Feb
30 ruary 9, 1935.
The generators, however, are
not limited to any particular type, and further
more, by virtue of the automatic fade-out con
trol system of this invention, presently to be
described in detail, the generators, instead of
being continuously operative, as has heretofore
been the practice, may be entirely controlled or
driven by the output voltage of the video-fre
quency ampli?er so as to operate only when
proper synchronizing-frequency impulses are be
40
ing supplied thereto.
For supplying‘ operating potentials to the vari
ous electrodes of the tube N, there is provided a
voltage divider 32, adapted for connection to a
suitable direct-current power source, not shown,
and the several electrodes are connected to ap
propriate taps on the divider. Certain of these
taps, as, for instance, 32a, 32b and 320, for the
control grid 2 I, the screen 22 and the ?rst anode
23, respectively, are preferably manually adjust
able for regulating the initial bias voltages ap
plied to these electrodes and for controlling the
operation of the system, as will be presently
more fully described. Current for the cathode
heater i9 may be supplied in a conventional
manner by a suitable circuit, not shown.
There is also provided a sound-frequency
channel connected to the output of the oscillator
‘modulator l3 and comprising, in cascade, an
60
75
intermediate-frequency ampli?er 33, a detector
35, the audio-frequency ampli?er 35 .and sound
reproducer 36.
Since the system of Fig. 1, as thus .far de
scribed, is, in general, conventional and well
understood in the art, a detailed explanation of
its general operation is deemed unnecessary.
Brie?y, however, the vision- and sound-modu
lated carrier waves intercepted by the antenna
lB-—_ii are selected and ampli?ed in the radio
frequency ampli?er I2 and supplied to the oscil
lator-modulator l3, where the signals are con
verted to intermediate frequencies in the usual
manner. The output of the oscillator-modula
tor is delivered to the intermediate-frequency
ampli?ers l4 and 33. The ampli?er I4 is tuned
to select a vision-modulated intermediate-fre
shown at l and 1) respectively, and between the
line impulse peaks the variations in amplitude
represent the video-frequency details of each
line. The maxima in the envelope correspond 30
to black and the minima correspond to white, in
the scene.
‘
The video-frequencies of modulation derived
from the television, carrier by the detector I5 are
supplied to the video-frequency ampli?er 16 35
wherein they are ampli?ed and supplied in the
usual manner to the control grid 2! of the oath
ode-ray tube and to the scanning generators 30
and 3!.
.
In certain forms of the present invention, 40
which will be hereinafter described, a peak recti
?er is employed for selectively producing the
automatic fade-out control voltage in accordance
with synchronizing impulses present in the mod
ulation voltage output of the video-frequency
ampli?er. This recti?er, aswill be seen later,
functions in the Well-known manner to develop
a unidirectional voltage proportional to the
amplitude of the synchronizing impulse compo~
nents in the output of the video-frequency am 50
pli?er, as indicated by the line DC in Fig. 2b.
With the proper potentials supplied to the elec
trodes of tube I1, an electron beam is emitted
from the cathode 20 and its intensity is modu
lated or controlledv by the grid 2|, in accordance 55
with the video-frequency voltages impressed
thereon. The screen 22 serves to control the
average intensity of the beam in a manner here
inafter to be explained, while the ?rst anode 24
cooperates with the second anode 25 to accelerate 60
and focus the electron beam.
Saw-tooth voltage waves are generated in the
line-frequency generator 30 and applied to the
plates 26 to produce an electrostatic ?eld to de
?ect the beam in one direction, while saw-tooth 65
current Waves are generated in the picture-fre
quency generator 3i and are applied to the coils
21 to produce a magnetic ?eld of saw-tooth wave
form to de?ect the beam in a direction normal
to the de?ection by the plates 26. The well 70
known rectilinear scanning pattern is thus traced
on the screen by the beam. ‘In accordance with
the present invention, the generators 30 and 3|
are preferably so adjusted as to operate only when
synchronizing impulses are being supplied there-' 75
2,187,128
to. The operation of the generators 30 and 3| is voltage is a negative voltage proportional to the
controlled and synchronized with the correspond _ amplitude of the received carrier and its applica
ing scanning actions at the transmitter by the tion to the tubes of the ampli?er l4 controls their
impulse components of the modulation frequen
ampli?cation so as to maintain-the output of this
cies supplied by the amplifier l6. Suitable selec
ampli?er within'a relatively narrow range for re
tive circuits, not shown, may be provided in the ceived signals of a wide range of intensities and
input circuits of the generators 30 and 3|, in the above a predetermined value. _Thus, the opera
usual manner, for discriminating against unde
tion of the automatic contrast control, per se, is
essentially similar to the operation of the well
Referring now more particularly to the portion . known automatic ampli?cation control systems
of the system of Fig. 1 embodying the present of sound broadcast receivers, such, for example, 10
invention, an automatic fade-out control posi
as that shown in U. S. Patent No. 1,879,863 to
tive bias voltage is derived by recti?cation of a Harold A. Wheeler. It is chie?y in its coopera
sired impulse frequencies.
10
part of the line-frequency saw-tooth voltage out
15 put of the scanning generator 30.' For this pur
pose a recti?er 31 is provided, having an anode
38 and a cathode 39, the anode being connected
to the high voltage output terminal of the gen
erator 30 through a resistance 40 and a coupling
20 condenser 41 and to ,the adjustable tap'32b on
the voltage divider 32 through an isolating re
sistor 43. The cathode 38 is connected to ground
through a condenser 42.
A resistor 44 is con_
nected across the recti?er 31 to develop the
automatic fade-out control bias voltage output of
this recti?er. An initial positive biasing poten
tial is applied to the screen 22 from thetap 321)
on the voltage divider, through the path which
includes the resistors 43 and 44.
'
The biasing potential which is applied to the
screen 22 from the tap 32b is of such magnitude
and polarity that the electron beam is normally
insu?icient to illuminate the ?uorescent screen.
Whenever the generator 30 is in operation, how
35 ever, an additional bias voltage is developed by
'30
tive relation with the above-described automatic
fade-out control that the present invention is 15
concerned with the automatic contrast control.
In various of the systems embodying the present
invention, in order that the automatic fade-out
control voltages ‘may be developed at proper am
plitudes to function correctly, it is necessary that 20
the automatic contrast control function so as
properly to control the degree of ampli?cation of
the received carrier.
Where the receiver just described is employed
in systems in which alternate carrier waves have 25
vision and sound modulation, respectively, and
the receiver is properly tuned, the output of
the ampli?er 33 will be detected, ampli?ed and
reproduced as sound in the manner aforede
scribed.
When, however, the receiver is being 30
tuned through a range of such alternate carriers,
vision- and sound-modulated intermediate-fre
quency 'carriers will be present alternately in
each of the ampli?ers l4 and 33. As has been
seen, the automatic fade-out control will pre 35
the recti?er 31 across the resistor 44, and this . vent the screen 25 from being illuminated when
voltage is applied positively to the' screen 22 a sound-modulated carrier is present in the am
so as to raise-its potential. and permit the beam - pli?er 14, since such a carrier will not have the
to become sufficiently intense to illuminate the proper frequency components of modulation for
40
?uorescent screen.
.
The output voltage of the recti?er 31 may or
may not be proportional to the amplitude of the
received vision-modulated carrier wave, accord
ing to the design of the generator 30. As above
45 mentioned, in this embodiment of the invention
the generator 30 is preferably so designed that the
amplitude of the periodic voltage developed
therein and supplied to the recti?er 31 is sub
stantially independent of the amplitude of the
50 control voltage supplied to it from the video-fre
quency ampli?er 16, unless such control voltage
falls below a predetermined minimum, as dis
closed in aforementioned copending application,
Serial No. 5,781. Hence, the input voltage to the
55 recti?er 31 will be supplied only when the gen
erator 30 is operating, and automatic ‘fade-out
control voltage will be developed for illuminating
the screen 25 of the tube 11 only in the presence
of a received signal and without appreciable
60 gradation in the control of the screen illumina
tion. It will also be appreciated that the farther
removed the automatic fade-out control detector
is from the system input, the more independent
will be the amplitude of the automatic fade-out
65 control bias from the amplitude of the received
carrier and the more effective will be the pro
tection of the cathode-ray tube by the automatic
fade-out control.
'
For the purpose of controlling the contrast of
70 the picture detail, a unidirectional bias voltage is
derived by recti?cation of the intermediate-fre
quency carrier by the detector I5, and is supplied
to the control grids of one or more of the ampli
fying'tubes of the intermediate-frequency ‘am
75 pli?er l4. This automatic contrast control bias
e?ecting scanning and operation of the auto
40
matic fade-out control.
On the other hand, by virtue of a further
arrangement provided by the present invention,
the reproduction of noisy television signals by the
sound reproducer is prevented when the vision
modulation frequencies are present in the sound 45
channel of the receiver. This arrangement com
prises amplifying, selecting and detecting means,
arranged to control the audio-frequency ampli
?er 35. A part of the audio-frequency output of
the detector 34 is supplied through a coupling 50
condenser 46 to the grid 41 of a tube 45. In the
plate circuit of the tube 45 is e?ectively included
a selective circuit 48, which is tuned to the line
scanning frequency of the vision-modulated car
rier and comprises a condenser 49 and an in 55
ductance 50 coupled to a coil 5| connected in the
plate circuit. The tuned circuit 48 is connected
to a diode recti?er which may comprise an auxil
iary anode 52 and the cathode 53 of the tube 45,
60
which, as illustrated, may be of the diode-triode
type. The load circuit of the recti?er 52-—53
comprises a resistor 54 and by-pass condenser 55.
Suitable operating potentials are applied to the
plate 56 and grid 41 of the tube 45, as by bat
teries 51 and 58, respectively, and a blocking re 65
sistor 59 may be interposed in the connection to
the grid 41.
When vision-modulated intermediate’ frequen
cies are present in thev amplifier 33 and are
recti?ed by the detector 34, a part of the output 70
of the detector is impressed upon the grid 41
through the condenser 46 and ampli?ed in the
triode section of the tube 45. Voltage of the line
scanning frequency is then developed across the
75
5
9,187,188
circuit 48 and recti?ed by the diode 52-58,
producing a unidirectional biasing voltage across
the resistor 54 in the well-known manner. This
ampli?er 35 and acts to suppress the audio
source, indicated as +3 in the usual manner.
The output of the tube 65 is impressed upon a
primary winding 88 of a transformer, the sec
ondary winding 18 of which is tuned by a con
denser " to the fundamental of the line-fre
irequency ampli?er 35 andito silence the loud
speaker 38.
quency scanning impulses, thereby furnishing
particular selectivity to this frequency. The
biasing voltage is applied negatively, by way of
the isolating resistor 35a, to the control gridof
one or more of the tubes in the audio-frequency
It will be apparent that, in the system de
scribed with reference to Fig. 1, the automatic
fade-out control, the automatic contrast con
trol and the automatic sound control means
cooperate to permit tuning and control oi’ the
15 sound and vision channels of the receiver by a
single control means, that is, the usual tuningv
control, not shown. Furthermore, the sound
control means of the present invention obviously
may be employed in any system where sound
20 modulated and vision-modulated signals are pres
ent, even though they do not comprise alternate
10
carriers and even though the sound- and vision
receiving channels are tunable separately and
independently.
25
by-pass condenser 81, while a blocking resistor
88 may be included in the connection to the plate
~
In Figs. 3, 4 and 5 there are illustrated tele
vision receivers embodying modi?ed forms of the
invention. In each of these ?gures there is shown
an antenna circuit l8--ll for receiving and sup
plying the modulated carrier waves to a carrier
30 frequency ampli?er indicated schematically at
82.
This ampli?er may be a tuned radio-fre
quency ampli?er, but preferably comprises ‘a
.l‘adio-frequency ampli?er, a superheterodyne
detector, and an intermediate-frequency ampli
?er, similar to the corresponding sections de
scribed with reference to Fig. 1. Further, as in
Fig. 1, in each of Figs. 3, 4 and 5 there is provided
a detector l5, video-frequency ampli?er l8,
cathode-ray tube l1 and line-frequency and pic
40 ture-frequency generators 38 and 3|, which, ex
cept as hereinafter noted, are connected in the
same manner as the corresponding parts of Fig. 1.
It will be noted that in each of these three
?gures the cathode-ray tube I‘! has, for con
45 venience, been indicated schematically, but it
will be understood that the tube and the circuits
employed in connection therewith are substan
tially the same as the corresponding parts illus
trated in, and described in connection with, Fig.
50 1. Likewise, the synchronizing-frequency gener
ators 38, 3| shown in Figs. 3-5, may be substan
tially like those of Fig. 1.
While in the systems of Figs. 3, 4 and 5 sound
receiving and reproducing systems have not been
55 shown, it will be understood that, if desired, such
systems may be provided as parts of the receivers,
as described with reference to the embodiment of
the invention shown in Fig. 1, and may include
automatic sound control means cooperating with
60 the automatic fade-out control and automatic
contrast control arrangements of the three em
bodiments in question.
'
Referring now particularly to Fig. 3, there is
illustrated an embodiment
of the invention
whereby greater automatic fade-out control and
automatic contrast control bias voltages and se
lective operation of these controls are obtained
by amplifying and selecting a particular char
acteristic of the video-frequency ampli?er out
70 put. A part of the output of the ampli?er I8 is
supplied by way of a coupling condenser 63 and
an isolating resistor 84 to the control grid of a
tube 65, which is preferably ‘a conventional
pentode type ampli?er. The cathode circuit of
75 tube 65 may include a biasing resistor 86 and,
voltage developed across the circuit 18-11, which 10
is a maximum for such frequency, is recti?ed by
a diode 12, the load circuit of which includes
series-connected resistors 18 and 14 individually
shunted by by-pass condensers 15 and 18, re
spectively, the junction between the two con
densers and the two resistors being grounded.
15
When the receiver is tuned to a vision-modu
lated carrier including proper synchronizing
impulses, line-frequency voltage is applied to the
recti?er 12, and a unidirectional voltage is de 20
veloped across the resistor 14 which is applied
positively, by way of a large time-constant ?lter
including series resistor 11 and a, by-pass con
denser 18, to a control electrode of the cathode
tube l1 to provide automatic fade-out control, 25
‘as described with reference to Fig. 1. A unidi- rectional voltage, ordinarily furnished from the
main direct-current power supply, but here rep
resented as furnished by battery 18a is applied
to the control electrode to provide an initial bias. 30
At the same time, a second unidirectional bias
voltage is developed vacross the resistor 13 which
is applied negatively, through a large time-con
stant circuit including a series resistor 18 and a
by-pass condenser 88, to the control grid of one 35
or more, of the tubes of the carrier-frequency
ampli?er 82, to provide automatic contrast con
trol for the system.
‘
It is believed that the operation of the auto
matic fade-out control and automatic contrast 40
control of the receiver of Fig. 3 will be obvious,
in view of the detailed description hereinbefore
set forth with regard to the operation of the
corresponding controls of the receiver of Fig. 1.
The distinguishing characteristics of the receiv 45
er of Fig. 3 are that the recti?ed automatic fade—
out control and automatic contrast control
voltages are both obtained by rectifying, in a
single tube, an ampli?ed and selected part of the
video-frequency ampli?er output. With this
50
arrangement, the recti?ed automatic fade-out
control voltages are proportional to the received
carrier.
In Fig. 4 a television receiving system is shown
which embodies a form of the invention in which 55
a single detector performs the functions of de
veloping the video-frequencies of modulation,. as
well as unidirectional automatic fade-out con
trol and automatic contrast control voltages. In
this arrangement, the output of the ampli?er 82 60
is recti?ed by a diode detector 8| comprising an
anode 82 and cathode 83. The load circuit of
the recti?er 8| comprises serially-connected re
sistors 84 and 85 across which are individually
connected the condensers 86 and 81, respec 65
tively. The junction between condensers 86 and
81 and resistors 84 and 85 is grounded. A low
pass ?lter is provided by a series inductance 88,
shunt condensers 81, 89, and shunt resistors 85
and 98, across which are developed both the 70
unidirectional automatic fade-out control and
the modulation voltages, including the video-fre
quencies and synchronizing frequencies. The
modulation-frequency output of this ?lter is con
nected through coupling condensers ill, 92 and 75
6
-
2,187,188
93 to the ampli?er I6, generator 3|, and gener
ator 30, respectively, The unidirectional volt
age component or the output of this ?lter, devel
oped across the resistor 90, is proportional to the
amplitude 01 the carrier output of the ampli?er
82. This voltage is applied positively, by way of
a large time-constant circuit including a series
resistor 94 and a by-pass condenser 95, and
through a suitable blocking resistor 85a, to a
10 control electrode, preferably the control grid of
the cathode-ray tube H to provide automatic
fade-out control In substantially the same man
ner as described with reference to Figs. 1 and 3.
A unidirectional voltage, ordinarily furnished
15 from the main direct-current power supply, but
‘ here represented as furnished by battery 90a is
applied to the control grid of the tube H to pro
vide an initial bias voltage. The large time-con
stant circuit in this instance serves to cut oil‘
20 the modulation frequencies supplied from the
detector 8|, so that they will not affect the oper
ation of the automatic fade-out control.
A second unidirectional voltage, which is also
proportional to the amplitude of the carrierout
25 put of the ampli?er 62, is developed across the
resistor 84 and is applied negatively, by way of
a large time-constant circuit including a series
‘resistor 96 and a by-pass condenser 97, to the
control grids of one or more of the tubes of the
of the ampli?er 62. as described with reference
to the other automatic contrast control circuits.
The diode tube 99 and its circuit connections
provide a peak detector the operation or which is
well known, so that a detailed description thereof
is deemed unnecessary here. Reference, how
ever, may be had to United States Patent No.
1,951,685 granted March 20, 1934, upon the ap
plication of Harold A. Wheeler, for a full de
scription of the operation of such a detector. 10
Such a peak detector as here utilized provides a
unidirectional voltage which is proportional to
the amplitude oi! the synchronizing impulses pres
ent in the modulation voltage impressed thereon
from the video-frequency ampli?er. The deri 15
vation of such voltages will be readily under
stood when it is considered, as hereinbefore
pointed out, that the result of applying the mod
ulation voltage illustrated in Fig. 2a to a peak
type of detector, is to develop a unidirectional 20
voltage proportional to the peak values of the
applied voltage, as is indicated, for instance, by
the line DC in Fig. 2b. The diode detector is
therefore poled so that its input voltage, during
the occurrence of impulse peaks, will make the 25
anode oi.’ the detector positive relative to the
cathode and thus develop across the load circuit,
that is, the resistors I03 and I04, unidirectional
voltages which are proportional to the value oi.’
ampli?er 62, to provide the automatic contrast
these peak impulses.
control in substantially the same manner as in
In the arrangement described with reference to
Fig. 5, it is assumed that the amplitude of the
impulse peaks relative to the unmodulated carrier
the previously described embodiments of the in
vention. It will be seen that in the embodiment
of Fig. 4, a single detector serves to supply the
35 video-frequencies as well as the unidirectional
automatic fade-out control and automatic con
trast control voltages. Here, however, there is
no selectivity with regard to the frequencies
from which the automatic fade-out control volt
40 ages are produced, and it is assumed that this
arrangement will be employed only where all of
the carrier frequencies of the spectrum through
which the receiver is tunable are vision-modu
lated as distinguished from systems wherein this
45 spectrum is occupied by carriers some of which
are modulated by sound and some by vision
frequencies.
30
amplitude, that is, the impulse percentage modu
lation, is uniform for ‘all of the television signals 35
which may be tuned in. Thus, the bias devel
oped by the detector 99 is, for all stations re-v
ceived, proportional to the carrier amplitude of
the output of the ampli?er i5. Since this is
the same condition as with the recti?er of Fig. 3, 40
which is utilized to develop the automatic fade
out control and automatic contrast control bias,
the same type of control is accomplished in the
receiver of Fig. 5 as in the receiver of Fig. 3.
By adjusting the peak detector so that only syn 45
chronizing modulation impulses are recti?ed, the
functioning of the automatic fade-out control
is made selective so that the positive automatic
fade-out control bias voltage is not developed and
In Fig. ,5, a television receiver is illustrated
which embodies still another form of the inven
50 tion. In this embodiment, the automatic fade ' no background illumination is provided for the
out control and automatic contrast control ‘uni
screen unless a properly modulated television
directional voltages are derived from an output carrier is being received. Hence, the scanning
of the video-frequency ampli?er I6. For this generators in this embodiment also may be con
purpose, a portion of the output voltage from a trolled by the video-frequency ampli?er output
55 point vin the video-frequency ampli?er I6 at to operate only when a properly modulated car
which the impulse peaks are positive relative rier is being received.
to ground is supplied, through a coupling con
While we have described what we at present
denser 98, to a diode recti?er 99 comprising an consider the preferred embodiments of our in
anode I00 and a cathode IOI. The load circuit vention, it will be obvious to those skilled in the
60 of the recti?er 99 includes a resistor I02 shunted art that various changes and modi?cations may
by a condenser I03. The remainder of the load be made therein without departing from our in
circuit is constituted by a resistor I04. The unl
vention, and we, therefore, aim in the appended
_ directional voltage developed across the resistor claims to cover all such changes and modi?cations
I02 is applied positively, through a large time
as fall within the true spirit and scope of our
65 constant circuit including a series resistor I05 invention.
and a by-pass condenser I06, to a control elec
What is claimed is:
trode of the cathode-ray tube I‘! to provide auto
1. A television receiving system for carrier
matic fade-out control therefor in the same man
waves of the type having modulation including
ner as in the aforedescribed embodiments of the video-frequency and synchronizing-frequency
70 invention.
components, comprising means for selecting, am
The unidirectional voltage developed across the plifying and detecting a received wave of said
resistor I04 is applied negatively, by way of a type to derive therefrom the modulation voltages,
large time-constant circuit including a series re
a. cathode-ray tube, means for exciting an elec
sistor I01 and a by-pass condenser I08, to the trode of said tube with the video-frequency com
75 control electrodes of one or more of the tubes ponents of said modulation voltages to control the
55
60
65
70
75
2,187,128
intensity of the cathode ray, means comprising
line-frequency and picture-frequency scanning
7
for utilizing said unidirectional voltage for con
trolling the average intensity of said beam.
5. A television receiving system for carrier
generator circuits controlled by the synchroniz
ing-frequency components of said modulation
voltages for effecting scanning by said cathode
type having modulation including video-frequency
ray, said cathode-ray tube having an additional
electrode for controlling the average intensity of
and synchronizing~frequency components, com
prising means for selecting, amplifying and de
said cathode ray, a large time-constant recti?er
tecting a received wave of said type to derive
therefrom the modulation voltages, a screen, a
source of a scanning beam for said screen, means
circuit excited from the line-frequency generator
10 circuit and including a resistor in its output cir
cuit, and a biasing circuit for said additional
electrode including a source of biasing voltage
ine?‘ective to establish or maintain the cathode
ray and including also said resistor, so connected
15 and proportioned that the resultant voltage oi.’
waves within a wide range of intensities and of the
controlled by the synchronizing-frequency com
ponents of said modulation voltages for effecting
scanning of said screen by said beam, means re
sponsive to the video-frequency components of
said modulation voltages for effecting variations
said bias circuit is effective to initiate said cath- - in the intensity of said beam to reproduce a scene, '
ode ray only during operation of said line-fre
an auxiliary ampli?er connected to amplify a por
quency generator.
tion of the output of said amplifying means, a
2. A television receiving system for carrier recti?er, and a selective circuit, tuned to a fre
waves of the type having modulation including
video-frequency
and
synchronizing-frequency’
components, comprising means for selecting, am
plifying and detecting a received wave or said
type to derive therefrom the modulation voltages,
25 a screen, and a source of a scanning beam there-'
for, means controlled by the synchronizing-fre
quency components of said modulation voltages
for eiTecting scanning of said screen by said beam,
means responsive to the video-frequency compo
30 nents of said modulation voltages for effecting va
riations in the intensity of said beam to repro
duce a scene, an auxiliary ampli?er connected to
quency of one of, said modulation voltages, 20
coupling said ampli?er and said recti?er, means
for utilizing a part of the output of said recti?er
for controlling the average intensity of said beam,
and means for utilizing another part of the out
put of said recti?er for maintaining the ampli
tude of said modulation voltages within a narrow
range relative to that of thereceived signals.
6. A television receiving system for carrier
waves within a wide range of intensities and of
the type having modulation'including video-fre 30
quency and synchronizing-frequency compon
ents, comprising means for selecting and ampli
amplify a portion of said modulation voltages, a‘
recti?er, and a selective circuit, tuned to said
fying a received wave of said type, means for
line-frequency modulation component, coupling
derive therefrom the modulation voltages, a
screen, a source of electrons for providing a
scanning beam for said carrier wave, means con
said ampli?er and said recti?er, and means for
utilizing the output of said recti?er for modifying
the average intensity of said beam.
3. A television receiving system for carrier
40 waves of the type having modulation including
video-frequency and synchronizing-frequency
detecting the output of said amplifying means to
trolled by the synchronizing-frequency compon
ents of said modulation voltages for effecting
scanning of said screen by said beam, means re
sponsive to the video-frequency components of
components, comprising means for selecting, am
said modulation voltages for e?'ecting variations
plifying and detecting a received wave to derive . in the intensity of said beam to reproduce a
therefrom the modulation voltages, a screen, a scene, an auxiliary ampli?er connected to ampli
45 source of a scanning beam for said screen, means fy a portion of the output of said amplifying
controlled by the synchronizing-frequency com
means, a recti?er, and a selective circuit, tuned
ponents of said modulation voltages for effecting
scanning of said screen by said beam, means re
sponsive to the video-frequency components of
said modulation voltages for effecting variations
in the intensity of said beam to reproduce a scene,
‘a peak voltage recti?er for rectifying the modu
lation voltages to derive therefrom a unidirec
tional voltage, and means for utilizing said uni
55 directional vpltage for controlling the average in
tensity of said beam.
4. A television receiving system for carrier
waves of the type having modulation including
video-frequency and line-frequency-synchroniz
60 ing and picture-frequency-synchronizing compon
ents, comprising means for selecting, amplifying
and detecting a received wave to derive therefrom
the modulation voltages, a screen, a source of a
scanning beam for said screen, means controlled
65 by said synchronizing-frequency components of
the modulation voltages for effecting scanning of
said screen by said beam, means responsive to the
video-frequency components of said modulation
voltages for effecting variation in the intensity of
70 said beam to reproduce a scene, a peak voltage
recti?er, means for supplying said line-fre
quency-synchronizin‘g components to said recti?er
to develop a unidirectional voltage of an amplitude
substantially equal to the amplitude of said line
75 frequency-synchronizing components, and means
to the line-frequency modulation component,
coupling said ampli?er and recti?er, means for
utilizing a part of the output of said recti?er for
modifying the average intensity of said beam,
and means for utilizing another part of the out
put of said recti?er for maintaining the ampli
tude of said modulation voltages within a nar
row range relative to that of the received signals.
7. A television receiving system for carrier
waves of the type having modulation including
video-frequency and synchronizing-frequency
components, comprising means for selecting and
amplifying a received wave of said type, a single
recti?er for deriving from the ampli?er carrier
wave the modulation voltages and a plurality
of unidirectional voltages, a screen, a source of
a scanning beam for said screen, means con
trolled by the synchronizing-frequency compo
nents of said modulation voltages for effecting 65
scanning of said screen by said beam, means re
sponsive to the video-frequency components of
said modulation voltages for eifecting variations
in the intensity of said beam to reproduce a
scene, means controlled by one of said unidirec
70
tional voltages for modifying the average inten
sity of the beam, and means controlled by an
other of said unidirectional voltages for main
taining the amplitude of said modulation volt 75
8
i
V
9,187,188
ages, within a narrow range relative to that of
the received signals.
.
8. A television receiving system for carrier
' waves of the type‘ having modulation including
5
video-frequency and synchronizing-frequency
components, comprising means for selecting, am
plifying and detecting a received wave of said
type to derive therefrom the modulation volt
ages, a screen, a source of a scanning beam for
10 said screen, means controlled by the synchro
ulation voltages, means for converting said
_ audio-frequency voltages into sound, a video
channel including means for detecting the am
pli?ed waves of said second type to derive there
from video-frequency and synchronizing-fre
quency modulation voltages, a screen, a source
of a scanning beam for said screen, means con
trolled by the synchronizing-frequency compo
nents of said modulation voltages for effecting
scanning of said screen by said beam, means re
10
nizing-frequency components of said modulation sponsive to the video-frequency components of
voltages for e?ecting scanning of said screen said voltages for e?'ecting variations in the in
by said beam, means responsive to the video
tensity of said beam to reproduce a scene, means
frequency components of said modulation volt
operative in accordance with the operation of
15 ages for effecting variations of the intensity of
said scanning means for modifying the average
said beam to reproduce a scene, a peak detector intensity of said beam, means responsive to the 15
connected to the output of said amplifying means amplitude of the received carrier of the second
for producing unidirectional voltages, means for ' said type for maintaining the amplitude of said
utilizing one of said unidirectional voltages for modulation voltages thereof within ‘a narrow
20 modifying the average intensity of the beam,
range relative to that of said received carrier, 20
and means for utilizing another of said unidirec
and means responsive to the presence of video
tional voltages for maintaining the amplitude frequencies in said audio channel for preventing
of said modulation voltages within a narrow the reproduction of sound.
range relative to that of the received signals.
11. A television receiving system for carrier
25
9. A television receiving system for carrier waves of a ?rst type having modulation includ
waves of a ?rst type having modulation com
prising sound frequencies and carrier waves of
a second type having modulation including
video-frequency and synchronizing-frequency
30 components, comprising a common means for
selecting and amplifying received waves of both
of said types, an audio channel including means
for detecting the ampli?ed waves of said ?rst
type to derive therefrom audio-frequency modu
35 lation voltages, means for converting said audio
frequency voltages into sound, a video-frequency
channel including means for detecting the am
pli?ed waves of said second type to derive there
40
from the video-frequency modulation voltages
and synchronizing-frequency modulation volt
ages, a screen, a source of a scanning beam for
said screen, means controlled by the synchroniz
ing-frequency components of said modulation
voltages for effecting scanning of said screen by
said beam, means responsive to the video-fre
Dquency components of said modulation voltages
for effecting variations in the intensity of said
beam to reproduce a scene, means operative in
accordance with the operation of said scanning
50 means for modifying the average intensity of
said beam, and means responsive to the presence
of video-frequencies in said audio channel for
preventing the reproduction of sound.
10. A television receiving system for carrier
waves of a ?rst type having modulation compris
ing sound frequencies and carrier waves of a
second type having modulation including video
frequency and synchronizing-frequency com
ponents, comprising a common means for select
ing and amplifying received waves of both of
said types, an audio channel including means
for detecting the ampli?ed waves of said ?rst
type to derive therefrom audio-frequency mod
ing video-frequency and synchronizing-frequen
25
cy components, and carrier waves of a second
type having modulation comprising sound fre
quencies, comprising a common means for se
lecting and amplifying carrier waves of both of 30
said types, oscillator-modulator means for heter
odyning said carrier waves, means for amplify
ing the intermediate-frequency voltages derived
by said heterodyning from the carrier waves of
said ?rst type, detecting and amplifying means 35
for said intermediate-frequency voltages to de
rive the modulation voltages, a screen, a source
of electrons for producing a scanning beam for
said screen, means controlled by the synchroniz
ing-frequency component of said modulation
voltages for e?ecting scanning of said screen by
said beam, means responsive to the video-fre
quency components of said modulation voltages
for effecting variations in the intensity of said
beam to reproduce a scene, means operative in
accordance with said scanning means for modi 45
fying the average intensity of said beam, means
for amplifying the intermediate-frequency_volt
ages derived by said heterodyning means from the
carrier waves of said second type, detecting and
amplifying means for the last said intermedi 50
ate-frequency voltages to derive therefrom
audio-frequency voltages, means for amplifying
and reproducing said audio-frequency voltages,
means connected to the output of the audio
frequency detecting means for selecting video
frequencies therefrom and for producing a uni
directional voltage, and means for utilizing said
unidirectional voltage to suppress ampli?cation
in said audio-frequency amplifying means.
_HAROLD M. LEWIS.
MADISON CAWEIN.
55
DlSCLAlMER
2,137,123.—Har0ld M. Lewis, Douglaston, Long Island, and Madison Gawain,
Manhasset, N. Y. TELEVISION SYSTEM. Patent dated November 15,
1938. Disclaimer ?led June 17, 1940, by the inventors; the assignee,
Hazelt'ine Corporation, assenting.
Hereby enter this disclaimer to the subject matter of claim 3 and the subject
matter of claim 4 insofar as the phrase ‘p‘ amplitude of said line-frequency-synchronizing
components” is construed to refer to the amplitude of said line-frequency-synchroniz
ing components as modi?ed by other components of the television signal, such as the
unidirectional background-illumination components thereof.
[Q?ic'ial Gazette July 9, 1940.]
DISCLAIMER
2,137,123.—Harold M. Lewis, Douglaston, Long Island, and Madison Gawain,
Manhasset, N. Y. TELEVISION SYSTEM. Patent dated November 15,
1938. Disclaimer ?led June 17, 1940, by the inventors; the assignee,
Hazeltine Corporation, assenting.
Hereb enter this disclaimer to the subject matter of claim 3 and the subject
matter of
4 insofar as the phrase ‘_‘ amplitude of said line-frequency-synchronizing
components” is construed to refer to the amplitude of said line-frequency-synchronjz
ing components as modi?ed by other components of the television signal, such as the
'directional background-illun?nation components thereof.
[O?cial Gazette July 9, 1940.]
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