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Патент USA US2406382

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‘Aug. 27, 1946.
' 2,406,382
Filled sept. 24, 1941
3 Sheets-Sheet 1
FIG. /
Aug. 27, 1946.
- 2,406,382
Filed SeptT 24, 1941
3 Sheet's—Sheet 2
Aug. 27, i946.)
_ ~2,406,382
, Filed Sept. 24, 1941
3 Sheets-Sheet 3
do "'\~
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\ . .
Patented Aug. 27, 1946
William M. Kellogg, Morristown, N. J., assignor
to Bell Telephone Laboratories, Incorporated,
New York, N. Y., a corporation of New York
7 Application September/'24, 1941, Serial No. 412,099
1 Claim. (Cl. 315-24)
This invention relates to an indicating system
and particularly to an indicating system employ
ing a cathode ray tube.
It is well known in the art to employ a cathode
ray tube as a timing device to indicate the time
intervals between a particular sequence of sig
nals. In such systems, the cathode ray beam gen
erated in the tube is de?ected by means of a
varying voltage applied to' one set of de?ection
elements so that it sweeps at a known rate over
a predetermined path on a screen or target to
. provide a linear time scale or axis and the signals
are applied to another set of de?ection elements
in such manner as to cause transverse de?ections
The various features and objects of the inven
tion will be better understood from the follow
ing detailed description when read in conjunc
tion with the accompanying drawings in which:
Fig. 1 shows a block diagram of one system in
accordance with the invention;
Fig. 2 shows schematically a more detailed ar
rangement of a system embodying the invention;
Fig. 3 shows curves which illustrate the indi
vidual and combined performance of the com
ponent elements of the system of Fig. 2.
In the arrangement of Fig. 1, the conventional
sweep generator A produces a saw-tooth voltage
of the beam from its normal path. The disposi 15 output wave, such as indicated on the ?gure by
the curve just below generator A, when it is ex
tion of the latter de?ections along the normal
cited by the sinusoidal voltage 8A of given fre
path as displayed on the screen indicates the time
quency applied to its input from the output of the
intervals existing between the signals.
control wave source CS. The saw-tooth voltage
In order‘ that individual signals or restricted
output of generator A is applied to the input
portions of the time scale of the cathode ray 20
(sweep de?ection elements) of the cathode ray
tube indicator tube may be closely observed, it
oscilloscope 0. If this sweep alone is applied to
is necessary in general to expand the scale beyond
the oscilloscope O, the cathode ray beam pro
the available range of the screen. As a result of
duced by the latter would progress uniformly
such sweep expansion, much of the total sweep
from left to right across the oscilloscope screen
range would be lost from View.
during the time interval H to 12 at a rate estab
An object of the invention is to expand a por
lished by the shape of the line Il-l2 in the ap
tion of the timing scale of an indicating circuit
plied saw-tooth wave. In order to increase this
employing a cathode ray indicator tube. A more
rate by the usual method, it would be necessary
speci?c object is to magnify or enlarge any de
sired restricted portion of the signal pattern as ' 80 to increase the amplitude Ill-l I, and as a re
sult, the amplitude of the sweep would be carried
viewed on the screen of a cathode ray indicator
beyond the capacity of the oscilloscope screen
tube while maintaining the total sweep range of
to reproduce it.
the cathode ray beam within the ?eld of view of
In accordance with the invention, an increase
the screen, thus obtaining an e?ect analogous
in the rate of the sweep over a portion of its
to that obtained by applying an optical lens to 35 range
without changing the total sweep range is
a limited segment of the scale of a slide rule.
by applying to the input (sweep de?ec
These objects are attained in accordance with
of the oscilloscope O, the output
‘one modi?cation of the invention by applying the
of an auxiliary sweep generator B, synchronized
combined output of two synchronized sweep (saw
with the ?rst generator, producing a saw-tooth
tooth) wave generators to the sweep de?ection 40
of a particular characteristic. As indicated
elements of a cathode ray oscilloscope, one oi
by the curve below the generator B, the latter
which is the usual linear full scale generator
saw-tooth wave may have a positive slope from
which drives the cathode ray beam from left to
2|! to 2i and a negative slope from 2| to 22, the
right across the screen, and the other having a
left-to-right component of only short duration 45 positive slope from 20 to 2| being steeper than
as compared with the ?rst generator. The re
stricted expansion or lens effect on the horizontal
scale is obtained during the interval of additive
e?ect of the two generators. The particular por
that from H to I 2 in the output wave of gen
erator A. The output wave of the sweep gener
ator B is transmitted through a suitable ampli
?er AM with an associated gain control for ad
tion of the sweep pattern to. which this lens effect 50 justing the amount of expansion, before applying
it to the oscilloscope sweep de?ection elements.
combination of the output waves of the two
ing the relative phase of the two sweep gener
which are applied to the oscilloscope
ators, this control being analogous to that ob
O is shown by the lower curve of Fig. 1, the
tained by moving an optical lens along the scale
65 chosen phase relationship between the two sweep
of a slide rule.
‘is applied may be controlled by suitably adjust
generators being such as to provide a 180 de
grees phase difference. Thus, it will be observed
that the positive interval I to 4 in the combina
tion wave is composed of intervals l-Z and 3-4
of less slope than the ll-IZ slope of the posi
tive interval of the output wave of generator A
and 2—3 of greater slope than ll—|2. The re
sult is that the interval 2—3 is expanded and
signals occurring during this time interval occu
py a magni?ed portion of the sweep trace of os
cilloscope O. The remaining intervals I-2 and
3-4 are compressed to the extent that 2—3' is
expanded so that the full scale de?ection of the
sweep remains constant.
y, _
The time interval 20—2| of the expansion pro
vided by sweep generator 13 is controlled by the
shape of the distorted voltage operating pulse
produced by the pulse generator PG from the.
sinusoidal voltage wave eB applied from the source
resistances l1, l8 in the control grid-cathode cir
cuit of tubes V1 and V4, respectively, these tubes
are over-driven by the large grid signal inputs
e1 and as, respectively, so that the signals in the
plate-cathode circuits of these tubes approxi
mate wave signals, as shown by e; of Fig. 3 (b)
' and es of Fig. 3 (c) , respectively.
The coupling condenser l9 between the plate
of tube V1 and the control grid of tube V2, and
the coupling condenser 23 between the plate of
tube V4 and the control grid of tube V5 are con
trolling impedances as compared with the asso
ciated grid coupling resistances 24, 25 and 26, 21,
respectively, and therefore cause the grid signal
voltages es and es applied to tubes V2 and V5,
to be the di?erentials of the plate signal voltages
ex. and c4 of tubes V1 and V4, respectively. The
former signal voltages, therefore, have pulse char
acteristics. The voltages es and 6e are shown in
CS to the input of the latter through the phase 20 Fig.
3 (c) and Fig. 3 (b), respectively. The
shifter PS. By suitable design of pulse generator
voltage es is required only to ?re the sweep gen
PG, the expansion interval may be made large,
erator vs with precision. The voltage e5’ applied
or it may be made small so that a very short
the control grid of tube V2 controls the interval
time interval is made to cover the full scale of
the oscilloscope O. The phase shifter PS is pro 25 of sweep expansion. The pulse characteristics of
65 are determined by the amplitude» of the control
vided for those applications in which it is re
grid voltage driving tube V1. The greater this
quired to shift the expansion interval along the
pulse duration, the longer the interval of, sweep
entire sweep interval.
expansion. The tube V2 is biased below cut-off
_ Fig. 2 shows in more detail circuits which may
so that‘ only the positive pulse intervals of the
be used to provide the restricted sweep expansion
applied voltage as will affect the plate current of
in accordance with the invention. In the system
This results in the discharge of condenser
of Fig. 2, the oscilloscope comprises a cathode
28 during the positive grid intervals and its re~
ray tube 6 in which are disposed the usual cath
charge through resistance 30 during the inter
ode ray beam producing and control apparatus
1, a pair of vertical de?ection plates 8, a pair of 35 vals between positive grid pulses. The resulting
saw-tooth voltage-developed across resistance 30
horizontal de?ection plates 9' and a ?uorescent
is shown as 67 in Fig. 3 (d). The tube V3 am
screen l3. The output ofva receiver M for de
pli?es the portion of this voltage appearing in
tecting the signals to be displayed on the screen
resistance 3| connected across condensers '28 and
of the oscilloscope is connected through the sig
nal ampli?er [5 across the vertical de?ection 40 29." The output of V3 and hence the degree of
mid-scale expansion may be controlled by ad
plates 8, causing the vertical de?ections of the
justment of the variable resistance 32 in the plate
cathode ray beam proportional to the varying po
cathode circuit of that tube. The output voltage
tentials of the received signals, along the timing
of tube V3 is shown as em in Fig. 3 (f) .
base line formed by the horizontal sweep of the
Similarly, the tube V5 will operate in response to
beam across the screen under control of the sweep 45
the pulse wave es applied to its control grid to
voltage applied to the- horizontal de?ection
cause the discharge of condenser‘ 33 during the
plates 9.
positive grid intervals and to recharge that con
In the arrangement of Fig. 2, the resistance
denser slowly through resistance 34 between
capacity coupled three-electrode vacuum tubes
The resulting saw-tooth voltage is shown
vV1, V2 and V3 corresponding in function to the 50 pulses.
as ea in Fig. 3 (e) .
pulse generator PG, the sweep generator B and
The saw-tooth voltage output e10 developed
the ampli?er AM with its associated gain con
by tube V5 and the expansion sweep voltage 68
trol, respectively, in the system of Fig. 1, are em
produced by tube V3 are combined in the control
ployed to produce the auxiliary sweep B of the
grid-cathode circuit of sweep ampli?er tube V6
cathode ray beam for expansion, and the resist 55 to form voltage (211 as shown in Fig. 3 (g), which
4 ance-capacity coupled three-electrode vacuum
is ampli?ed by ampli?er V6 and applied across
tubes V4 and V5, corresponding in combined func
the horizontal de?ection plates 9 of the cath~
tion to the sweep generator A in the system of
ode ray tube 6. The expansion interval occurs
Fig. 1, are employed to produce the main full
mid-scale of the sweep voltage. As noted
scale sweep A of the beam. With this arrange 60
above, it is under control of the variable cou
ment, the expansion interval is placed at mid
pling resistance 32 in the plate circuit of tube
‘scale of the main sweep by operating the tubes
The dotted curves em’ in Fig. 3 (f) and en’
V1 and V4 at 180 degree phase relationship by
in Fig. 3 (9) show the effect of increasing this
connecting them in push-pull with respect to the
so that the expanded segment oc
applied constant frequency sinusoidal control 65 resistance
cupies the full scale of the oscilloscope. The
wave from source CS, and the phase'shifter PS
of the system Fig. l is omitted.
The operation of the system of Fig. 2 will be
explained by reference to the curves of Fig. 3.
Fig. 3 (a) shows the sinusoidal constant fre
quency‘voltages (21 and c2 with 180 degrees phase
di?erence between them respectively applied to
the control grid-cathode circuits of the tubes V1
and. V4 from the control wave source CS through
input transformer it. Because of the large series .
lower the setting of resistance 32, the more
nearly the‘ sweep voltage approaches a conven
tional saw-tooth sweep which‘ will cause the
cathode ray‘ beam in tube 6 to move at a uni
form rate from left 'to right over the screen l3.
As the amount of injected expansion is in
creased the faster the beam travels at mid-scale
and the slower at the other portions of the
screen. The 'eifect of the combination is‘ a
center expansion and a corresponding‘ end com
pression of the oscilloscope signal pattern.
scale and a corresponding compression of the
‘ The whole signal pattern is thus kept in view as
remaining portion so as to maintain the total
sweep range within the ?eld of View of said
the center is expanded for close observation
of part of the pattern. It is thus possible to
monitor the full sweep range, even though,
say 5 per cent of the scale is expanded to occupy
50 per cent of the full de?ection. By the use
of a suitable phase shifter, such as shown in
the alternative arrangement of Fig. 1 to pro
vide various adjustments of the phase rela
tions of the main sweep generator and the
auxiliary sweep generator, the expansion may
be applied to any desired portion of the sweep
screen and means for controlling the relative
phase of the outputs of said generators to se
lect the portion of the scale to be ampli?ed, said
one generator comprising an ampli?er having a
plurality of resistance-condenser coupled vacu
um tube stages, the second stage of which is
10 biased below cut-o?, means to apply a sinu
soidal voltage input to said ampli?er of sum
cient amplitude to overload the ?rst stage
thereby producing a square-shaped voltage out
put for that stage, the resistance-condenser
Various other modi?cations of the circuits 15 coupling between the ?rst two ampli?er stages
being proportioned so that the voltage input to
illustrated and described which are within the
the biased second stage is the di?erential of the
spirit and scope of the invention will be ap
voltage output of said first stage, thus producing
parent to persons skilled in the art.
a pulse output for said second stage which is
What is claimed is:
unaifected by the positive portions of the input
In combination with a cathode ray tube sig
voltage thereto, the condenser in the output
nal indicator including cathode ray beam pro
coupling of said second stage discharging dur
ducing and de?ecting means and an indicating
ing the positive input intervals and recharging
screen, two saw-tooth wave generators for con
through the resistance thereof during the in
trolling said deflecting means to sweep the
cathode ray beam back and forth across said 25 tervals between positive inputs, the gain of said
ampli?er being adjusted to provide the desired
screen to provide a time scale thereon, one 01”
degree of scale expansion and the amplitude of
said generators producing a saw-tooth wave, the
the sinusoidal voltage input thereto being se
rising portions of which are of relatively short
lected to control the pulse duration of the
duration compared with those produced by the
other generator, such that the combined action 30 ampli?er output applied to said de?ecting
of both generators on said de?ecting means re
sults in an expansion of a portion of said time
means and thusthe interval of scale expansion.
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