US2295330A - Television or other signal transmission system - Google Patents
Television or other signal transmission system Download PDFInfo
- Publication number
- US2295330A US2295330A US275367A US27536739A US2295330A US 2295330 A US2295330 A US 2295330A US 275367 A US275367 A US 275367A US 27536739 A US27536739 A US 27536739A US 2295330 A US2295330 A US 2295330A
- Authority
- US
- United States
- Prior art keywords
- signals
- signal
- picture
- auxiliary
- television
- Prior art date
- 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
Links
- 230000008054 signal transmission Effects 0.000 title description 4
- 230000003321 amplification Effects 0.000 description 12
- 238000003199 nucleic acid amplification method Methods 0.000 description 12
- 208000003443 Unconsciousness Diseases 0.000 description 11
- 230000005540 biological transmission Effects 0.000 description 6
- 230000008878 coupling Effects 0.000 description 4
- 238000010168 coupling process Methods 0.000 description 4
- 238000005859 coupling reaction Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 3
- 230000000306 recurrent effect Effects 0.000 description 3
- 230000004075 alteration Effects 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006641 stabilisation Effects 0.000 description 2
- 206010027146 Melanoderma Diseases 0.000 description 1
- 238000005513 bias potential Methods 0.000 description 1
- 238000010894 electron beam technology Methods 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 230000003019 stabilising effect Effects 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/14—Picture signal circuitry for video frequency region
- H04N5/16—Circuitry for reinsertion of DC and slowly varying components of signal; Circuitry for preservation of black or white level
- H04N5/165—Circuitry for reinsertion of DC and slowly varying components of signal; Circuitry for preservation of black or white level to maintain the black level constant
Definitions
- This invention relates to electric signal transmission systems and in particular to television systems in which it is desired to insert the D. C. or low frequency components into the television signals.
- an apparatus for stabilising a recurrent datum level in television or like signals having a recurrent reference amplitude which is related to but not equal to said datum level comprising means for adding to said signals prior to the point in the signal channel at which said datum level is stabilised, an auxiliary signal which substantially annuls the difference between said reference amplitude and said datum level, whereby the stabilisation of said datum level can be rendered substantially independent of changes in the gain of the signal channel prior to said point of stabilisation.
- said television or the like signal is generated by a cathode ray scanning tube
- said reference amplitudes are the signals produced during periods when the beam is cut off
- said auxiliary signals are similar to and generated simultaneously with signals used to cutoff said beam.
- said reference amplitudes are produced during the intervals between lines when the beam is cut oil, and said auxiliary signals are derived from the signals which cut off the beam.
- auxiliary signals are derived from the beam current of the scanning tube.
- the amplitude and/or sense of said auxiliary signals are preferably controlled so as to adjust the final level of the datum (or black) level of the signal after D. C. re-establshment.
- an auxiliary signal consisting of pulses similar in duration and timing to the black out pulses, that is, the pulses which are used to cut off the electron beam, is added to the signals prior to D. C. re-establishment, and these auxiliary pulses, if of sufiicient amplitude and of correct sense, change the blacked out signal amplitude so that it is coincident with black. Alteration of the signal amplitude, as by gain control, then no longer affects the D. C. level of black.
- Figure 1 shows a circuit for effecting such a. mixture.
- the arrow heads pointing upwardly or downwardly indicate that the leads to which the arrow heads are attached are connected respectively to suitable positive or negative potential supplies.
- the signals from the scanning tube are applied to terminal i and through a suitable coupling condenser and grid leak resistance to the grid of valve 3.
- the auxiliary signals are applied to the terminal 2 to the grid of valve 4 via a suitable coupling condenser and grid leak resistance.
- the cathodes and suppressor grids of valves 3 and 4 are earth'ed.
- the anodes of valves 3 and d are joined in parallel to a common anode load resistance, which is suitably decoupled by a resistance and condenser.
- the auxiliary signals may be line black out pulses, for example.
- FIG. 1 shows an alternative arrangement of the potentiometer which gives signals of either sense, In this figure a transformer winding is connected in parallel with the potentiometer 2a and the centre tap of the transformer is connected to earth, the auxiliary signals being applied at terminal 2. It can be seen that the signal produced across one half of the transformer is equal in magnitude, but of opposite sign, to that produced across the other half of the transformer.
- auxiliary pulses and the picture signals are mixed in the common anode circuit of valves 3 and 4 and pass through a suitable coupling condenser and grid leak resistance to the gain control stage 5, which comprises a variable-mu valve with bias controlled by potentiometer l, which is suitably decoupled by a condenser.
- the valve 5 is provided with an anode resistance and decoupling resistance and condenser andthe output is taken from terminal 6 for further amplification and D. C. re-establishment.
- the potentiometer 2a may be adjusted to give the correct black level out, it being assumed that the D. C. re-establish'ment device is adjusted to give the correct level when the modified blacked out signal is equal to the average black level.
- the signal input to the terminal I comprises the picture signal ii i and the average black signal H3 upon which is superimposed the spurious signal generated as above described by the blacking out of the beam.
- the auxiliary pulse signal supplied from the source I03 is shown at Ill and comprises a rectangular pulse similar to the .2 assumed spurious signal whose polarity is opposite to that of the signal H3 and whose amplitude is greater than that of H3.
- the output of the two tubes 3 and 4 therefore, shows the ampiified picture signal H5 which is merely a magn'liied replica of i l 1, together with the corrected black-out pulse H9 which represents the difference between H3 and H9.
- This signal is fed through the condenser 69 to the amplifier tube 5 which, from the terminal 6, feeds the D. C. inserter iii"! substantially the same wave form shown at lie-i it? with, however, greater amplitude due to the amplification of the tube 5.
- the tilt corrector Hi5 feeds into the terminal 9 a wave shape i228 which is substantially triangular for the assumed condition of the black spot increasing linearly with deflection.
- the output of the tube 8 fed from terminal ID has the identical wave shape of 52L except, of course, it is of greater amplitude and the output from tube 8 is combined with the output of the D. C. inserter as described above.
- Figure 2 shows an arrangement by which the auxiliary signals may be mixed in at the scanning tube, the arrangement being such that the auxiliary signals are automatically varied in accordance with the strength of scanning beam H represents a scanning tube of which only the signal plate connection [2, the cathode i3 of the gun, and the control grid M of the gun are shown.
- the signal plate is connected to a composite load consisting of a very high resistance i5 shunted by a lower resistance It in series with a condenser l'l.
- This composite arrangement gives a very large signal (as compared with IE alone) at low frequencies, thus reducing the effective flicker noise of the amplifier.
- the frequency distortion produced by this arrangement is corrected later.
- the cathode I3 is connected to the negative supply lead 18 through a resistance I9.
- the cathode I3 is also coupled through a condenser and leak to the grid of a valve 26 whose anode load is a variable resistance 2
- Valve 20 is provided with a suitable cathode biasing resistance.
- phase reversing valve can be inserted between l3 and 2
- the shift is proportional to the beam current.
- the method of television transmission which comprises supplying picture signals having direct current and alternating current components, which signals are recurrently'interrupted by a spurious signal related to the black level of the picture, adding auxiliary signals in substantially time coincidence to the spurious signals, the auxiliary signals being of such amplitude and polarity to give a resultant representative of the black level of the picture, manually controlling the amplification of the unsuppressed components of the picture signals in accordance with the picture signals and reinserting direct current components representative of the suppressed direct current components subsequent to the controlling of the amplification of the unsuppressed picture signals.
- the method of television transmission which comprises supplying picture signals having direct current and alternating current components, which signals are recurrently interrupted by a spurious signal related to the black level of the picture, adding auxiliary signals in substantially time coincidence to the spurious signals, the auxiliary signals being of such amplitude and polarity to give a resultant representative of the black level of the picture, manually controlling the amplification of the unsuppressed components of the picture signals in accordance with the picture signals, reinserting direct current components representative of the suppressed direct current components subsequent to the controlling of the amplification of the unsuppressed picture signals, supplying a second auxiliary signal, manually controlling the amplification of the second auxiliary signal in accordance with the picture signals, and subsequently combining the amplified auxiliary signal with the picture signal and the reinserted direct current components.
- a television transmission system comprising means for supplying picture signals having direct current and alternating current components, which signals are recurrently interrupted by a spurious signal related to the black level of the picture, means for adding auxiliary signals in substantially time coincidence to the spurious signals, the auxiliary signals being of such amplitude and polarity to give a resultant representative of the black level of the picture, means for manually controlling the amplification of the unsuppressed components of the picture signals in accordance with the picture signals, and means for reinserting direct current components representative of the suppressed direct current components subsequent to the controlling of the amplification of the unsuppressed picture signals.
- a television transmission system comprising means for supplying picture signals having direct current and alternating current components, which signals are recurrently interrupted by a spurious signal related to the black level of the picture, means for adding auxiliary signals in substantially time coincidence to the spurious signals, the auxiliary signals being of such am-.
- plitude and polarity to give a resultant representative of the black level of the picture
- means for manually controlling the amplification of the unsuppressed components of the picture signals in accordance with the picture signals means for reinserting direct current components representative of the suppressed direct current components subsequent to the controlling of the amplification of the unsuppressed picture signals, means for supplying a second auxiliary signal, means for manually controlling the amplification of the second auxiliary signal in accordance with the picture signals, and means for subsequently combining the amplified auxiliary signal with the picture signal and the reinserted direct current components.
- a television transmitter comprising a cathode ray tube having a cathode, control electrode, anode and target electrode, a power supply, a resistor connected between the power supply and said cathode, a first thermionic amplifier having a cathode, grid and plate, means to supply potential variations occurring across said resistor connected between the cathode and power supply to the grid and cathode of said thermionic amplifier, a resistor connected between said power supply and said target electrode, a connection from said resistor to the plate of said thermionic amplifier, a serially connected resistor and condenser connected in parallel with said resistor connected to said target electrode, a second thermionic amplifier having a cathode, grid and plate, and a connection from said target electrode to the grid of said second thermionic amplifier.
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Control Of Amplification And Gain Control (AREA)
- Picture Signal Circuits (AREA)
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB16080/38A GB515360A (en) | 1938-05-30 | 1938-05-30 | Improvements in or relating to television or other signal transmission systems |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US2295330A true US2295330A (en) | 1942-09-08 |
Family
ID=10070797
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US275367A Expired - Lifetime US2295330A (en) | 1938-05-30 | 1939-05-24 | Television or other signal transmission system |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US2295330A (fr) |
| FR (1) | FR855464A (fr) |
| GB (1) | GB515360A (fr) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2445040A (en) * | 1943-05-13 | 1948-07-13 | Rca Corp | Dark spot corrector |
| US2485310A (en) * | 1946-12-12 | 1949-10-18 | Du Mont Allen B Lab Inc | Video black clipper |
| US2543037A (en) * | 1946-01-07 | 1951-02-27 | Farnsworth Res Corp | Television receiver |
| US2620393A (en) * | 1948-07-15 | 1952-12-02 | Emi Ltd | Circuits for reinserting direct current and low-frequency components |
| US2658104A (en) * | 1949-12-30 | 1953-11-03 | Du Mont Allen B Lab Inc | Television shading signal and clamping circuit |
| US2753394A (en) * | 1949-05-19 | 1956-07-03 | Emi Ltd | Television transmission systems |
| US2908753A (en) * | 1954-01-23 | 1959-10-13 | Poutil R B V Et De La Radio In | Visual television transmitter |
-
1938
- 1938-05-30 GB GB16080/38A patent/GB515360A/en not_active Expired
-
1939
- 1939-05-24 US US275367A patent/US2295330A/en not_active Expired - Lifetime
- 1939-05-30 FR FR855464D patent/FR855464A/fr not_active Expired
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2445040A (en) * | 1943-05-13 | 1948-07-13 | Rca Corp | Dark spot corrector |
| US2543037A (en) * | 1946-01-07 | 1951-02-27 | Farnsworth Res Corp | Television receiver |
| US2485310A (en) * | 1946-12-12 | 1949-10-18 | Du Mont Allen B Lab Inc | Video black clipper |
| US2620393A (en) * | 1948-07-15 | 1952-12-02 | Emi Ltd | Circuits for reinserting direct current and low-frequency components |
| US2753394A (en) * | 1949-05-19 | 1956-07-03 | Emi Ltd | Television transmission systems |
| US2658104A (en) * | 1949-12-30 | 1953-11-03 | Du Mont Allen B Lab Inc | Television shading signal and clamping circuit |
| US2908753A (en) * | 1954-01-23 | 1959-10-13 | Poutil R B V Et De La Radio In | Visual television transmitter |
Also Published As
| Publication number | Publication date |
|---|---|
| FR855464A (fr) | 1940-05-11 |
| GB515360A (en) | 1939-12-04 |
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