US2177723A - Electrical segregation circuit - Google Patents

Electrical segregation circuit Download PDF

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Publication number
US2177723A
US2177723A US137166A US13716637A US2177723A US 2177723 A US2177723 A US 2177723A US 137166 A US137166 A US 137166A US 13716637 A US13716637 A US 13716637A US 2177723 A US2177723 A US 2177723A
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United States
Prior art keywords
signals
pulses
valve
anode
circuit
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US137166A
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English (en)
Inventor
Kemp Roland John
Fewings David John
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RCA Corp
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RCA Corp
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Publication date
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Publication of US2177723A publication Critical patent/US2177723A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/04—Synchronising
    • H04N5/08—Separation of synchronising signals from picture signals
    • H04N5/10—Separation of line synchronising signal from frame synchronising signal or vice versa

Definitions

  • This invention relates to television and like receivers and more particularly to synchronizing signal apparatus suitable for use in cathode ray tube television and like receivers.
  • frequency selective networks i. e. networks relying upon resonant circuits, and the like, for selecting the one type of synchronizing signal from the other but to in general such frequency selective networks are not very reliable nor effective. They are, moreover, not as simple as is desirable.
  • the object of the present invention is to provide improved and simplified apparatus for selecting framing signals from line synchronizing signals in a television or like receiver for cooperating with a transmitter of the kind transmitting two varieties of synchronizing signals of different lengths.
  • ap- 50 paratus in accordance with this invention does not involve the use of tuned circuits or like frequency selective means, but, nevertheless reliable selective action is provided.
  • this inven- 55 tion received line synchronizing signals and framing signals appearing in a common channel and distinguished from one another at least in that the two varieties of signals are of different duration or different amplitude, or both, 60 are separated by means including a selective device or circuit having an operating input voltage-output current curve of substantially different slope at different parts thereof.
  • the line synchronizing and framing signals as received are of the same amplitude they are first 5 applied to a time circuit network to derive therefrom different amplitude signals which are then applied to the selective device or network.
  • the synchronizing and framing signals are of different amplitudes they may be applied direct to the selective device or network.
  • the selective device or network is such as to transform different amplitude pulses into different polarity pulses.
  • FIG. 1 is an embodiment of our invention
  • Figs. 2 and 3 are explanatory curves
  • Fig. 4 is a modified arrangement
  • Fig. 5 is an explanatory curve
  • Fig. 6 is an application of our invention
  • Figs. '7, 8, and 9 are explanatory curves
  • Fig. 10 is an alternative arrangement
  • Fig. 11 is a further modified arrangement.
  • Fig. 1 which shows one way of carrying out this invention as applied to a system wherein the line synchronizing and framing signals as received are of the same amplitude but different durations, the mixed synchronizing signals are applied through a condenser l across a time constant circuit which may, for example, consist of a shunt resistance-condenser combination 2, 3, and which is inserted in the cathode lead of a screen grid valve 4 whose anode 5 is connected through a resistance 6 to a point I on an anode battery or other source 8, the screen grid 9 being connected through a resistance Ill to a point II which is positive with respect to the point I.
  • a condenser l across a time constant circuit which may, for example, consist of a shunt resistance-condenser combination 2, 3, and which is inserted in the cathode lead of a screen grid valve 4 whose anode 5 is connected through a resistance 6 to a point I on an anode battery or other source 8, the screen grid 9 being
  • the time constant circuit 2, 3, is so designed as to accept the relatively long period framing pulses and heavily to attenuate the relatively short period line synchronizing pulses.
  • the control grid l2 and cathode l3 are tied together.
  • the operating potentials applied to the screen grid valve are so chosen that the operating anode current (ordinates)- anode voltage (abscissae) characteristic curve of the valve is of the well known form represented in Figure 2, exhibiting a rising portion followed by a dip followed by a second more steeply rising portion which ultimately flattens out in the well known way.
  • the valve 4 is operated at a suitable point of this characteristic somewhere on the origin side of the dip e. g. at the point A which is at the crown of the first rise.
  • this time constant circuit 2, 3 will be to transform the pulses of similar amplitude but different duration into pulses of difierent amplitudes and short pulses (line synchronizing signals) being transformed into small amplitude pulses such as are represented at-L in Fig. 2 while the long pulses (framing signals) will be transformed into larger amplitude pulses such as are represented at F in Fig. 2.
  • the small amplitude pulses L (due to the line synchronizing signals) will cause a diminution of anode current in valve 4 (the valve swing occurring over the negative sloping portion BC of the dip) whereas the large amplitude pulses F will cause a rise in anode current since the valve swing carries over to a point such as B near the top of the second rising portion in the characteristic curve.
  • the line pulses appear in the anode circuit of the valve as of one polarity and the framing pulses appear of the opposite polarity.
  • the anode pulses may be applied directly or through a phase reversing valve to a rectifier circuit and obviously the rectified resultant will consist either of the line pulses only or of the framing pulses only according as to whether the energy channel to the rectifier includes a phase reversal valve or not.
  • the above described arrangement may be modified by deriving the one variety of pulse from the anode (through condenser I4) and the other from the screen grid 9 (for example through condenser l5) by means of suitable rectifier circuits energized from these two electrodes, for obviously the pulses from the screen grid will be in reversed phase as compared to those from the anode.
  • the screen grid valve and circuit is such that the operating characteristic is as shown in Fig. 3 rather than as shown in Fig. 2, i. e. such that the dip in the anode currentanode voltage curve extends below the abscissa line by an amount approximately equal to the amount by which the first rise in the curve extends above the abscissa line.
  • This will obviously result in improved sensitivity.
  • the mixed synchronizing signals of different duration are applied through a time constant circuit within the broken line rectangle TC to the screen grid 9 of a screen grid valve 4 which is so operated as to exhibit an anode current (ordinates)-screen grid voltage (abscissae) characteristic as shown in Fig. 5 said characteristic rising to a maximum and then falling away.
  • the operating point is chosen at a point such as G on the positively sloping part HGK of the curve so that the small amplitude signals such as L (due to short duration line signals) result in a swing up to or near the crown of the curve but the larger amplitude signals such as F (due to long, framing signals) cause a swing well past this point X and down to a point such as J near the abscissa line.
  • the control grid l2 and cathode' l3 are tied together and the time circuit again attenuates the short pulses just as in Fig. 1, being, however, now inserted in the signal supply lead tothe screen grid.
  • the mixed synchronizing signals which are arranged to have their peaks in the positive direction, are applied through a condenser I and regulating potentiometer I8 between control grid I6 and cathode ll of a triode I9 whose anode cathode space 20l1 is shunted by a condenser 2
  • the anode 20 of the triode receives positive potential from a tap 22 on a potentiometer resistance 23 shunted across a potential source (not shown) through a circuit including a resistance 6 and the anode-cathode space 5'--
  • anode current (ordinates) anode voltage (abscissae) characteristic curve as shown in Fig. 8 with a rising portion MN followed by a shallow, fairly flat bottomed dip NQ followed by a more steeply rising portion QP which ultimately flattens oil.
  • the operating point is chosen at a point such as 0 on the flat bottom of the dip so that the small increases of anode voltage due to line pulses produce little or no change in anode current (the valve swing remains on the fairly flat bottom NQ of the dip) whereas the large increases in anode voltage due to framing pulses swing the valve to or near the top of the second rise Q? in the curve thus causing large anode current changes. Accordingly framing pulses may be taken via con- &
  • the screen grid valve in the last described embodiment may be replaced by any other suitable charging device exhibiting an applied voltage (abscissae) output-current characteristic curve part of which consists (as shown in Fig. 9) v of a fairly flat portion followed by a rising portion which (preferably) flattens oif sharply at the top.
  • a suitably operated diode might replace the screen grid valve.
  • the screen grid valve might be replaced by a neon or other electric discharge lamp 25 as shown in Fig. 10.
  • the trlode l9 must be biased practically to out off and the arrangement made such that on switching on the anode.
  • A. circuit arrangement for separating television synchronizing or like signals which are of different time duration comprising means for transforming the signals of different time duration into signals of different amplitudes, a selective device comprising a thermi onic valve having an operating input voltageoutput current curve of substantially different slope at different parts and means for applying the transformed, amplitude-differentiated signals as input signals to said valve means for biasing said valve whereby signals of one amplitude sweep over a portion of its characteristic of substantially different slope from that swept over as a result of the application of signals of the other amplitude, the valve being so operated that the dip in the anode current-anode voltage curve extends below the abscissae line by an amount approximately equal to the amount by which the first rise in. the curve extends above the abscissae line.
  • a circuit arrangement for separating television synchronizing signals comprising a selective device including a valve having anode, cathode and at least one control electrode, said valve having an operating input voltage, output current curve of substantially different slope at different parts of the curve, a diode so operated that its anode current-anode voltage characteristic includes a fairly flat part followed by a steeply rising part, the operating point being chosen on the fairly flat part so that small increases of anode voltage produce little change in anode current whereas large increases of anode voltage cause substantial changes in anode current, said diode being connected in a.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Video Image Reproduction Devices For Color Tv Systems (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
US137166A 1936-04-29 1937-04-16 Electrical segregation circuit Expired - Lifetime US2177723A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB12215/36A GB472923A (en) 1936-04-29 1936-04-29 Improvements in or relating to television and like receivers

Publications (1)

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US2177723A true US2177723A (en) 1939-10-31

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ID=10000456

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Application Number Title Priority Date Filing Date
US137166A Expired - Lifetime US2177723A (en) 1936-04-29 1937-04-16 Electrical segregation circuit

Country Status (4)

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US (1) US2177723A (en:Method)
BE (1) BE421309A (en:Method)
DE (1) DE755830C (en:Method)
GB (1) GB472923A (en:Method)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2564554A (en) * 1947-10-09 1951-08-14 Rca Corp Background control and synchronizing signal separating circuit
US2597833A (en) * 1947-11-08 1952-05-20 Hazeltine Research Inc Pulse-signal translating arrangement
US2632049A (en) * 1949-06-18 1953-03-17 Zenith Radio Corp Signal slicing circuits
US3591824A (en) * 1969-03-05 1971-07-06 Madatron Inc Driving means for crt{3 s

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2564554A (en) * 1947-10-09 1951-08-14 Rca Corp Background control and synchronizing signal separating circuit
US2597833A (en) * 1947-11-08 1952-05-20 Hazeltine Research Inc Pulse-signal translating arrangement
US2632049A (en) * 1949-06-18 1953-03-17 Zenith Radio Corp Signal slicing circuits
US3591824A (en) * 1969-03-05 1971-07-06 Madatron Inc Driving means for crt{3 s

Also Published As

Publication number Publication date
DE755830C (de) 1953-06-22
GB472923A (en) 1937-10-04
BE421309A (en:Method)

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