US2124044A - Electrical apparatus - Google Patents

Electrical apparatus Download PDF

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Publication number
US2124044A
US2124044A US718354A US71835434A US2124044A US 2124044 A US2124044 A US 2124044A US 718354 A US718354 A US 718354A US 71835434 A US71835434 A US 71835434A US 2124044 A US2124044 A US 2124044A
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United States
Prior art keywords
amplifier
current
circuit
synchronizing
direct
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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
Application number
US718354A
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English (en)
Inventor
Arthur W Vance
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
RCA Corp
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RCA Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by RCA Corp filed Critical RCA Corp
Priority to US718354A priority Critical patent/US2124044A/en
Priority to FR787688D priority patent/FR787688A/fr
Priority to NL73060A priority patent/NL41139C/xx
Priority to GB10110/35A priority patent/GB454511A/en
Priority to DE1935R0092992 priority patent/DE701082C/de
Application granted granted Critical
Publication of US2124044A publication Critical patent/US2124044A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • 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

  • My invention relates to electrical signalling apparatus and particularly to direct-current ampliiiers.
  • Direct-current ampliiiers In many electrical circuits it has been found 5 desirable to utilize direct-current amplifiers rather than ampliiiers which can not transmit a direct-current component. Direct-current ampliiiers, however, have a serious defect in that they have a tendency to drift, That is, with no signal on the amplier, the output current will gradually increase or gradually decrease over a period of several minutes.
  • I provide a directcurrent amplier with a closed loop circuit so 3.3 connected that energy may be fed from the output circuit of the amplifier to its input circuit in the proper phase to oppose any change in voltage or current at the output circuit.
  • the signals to be ampliiied such as picture signals, are impressed upon the ampliiier input circuit periodically whereby there are intervals during which no signal is impressed thereon.
  • the loop circuit is so designed that it is ineffective during the period a signal is impressed upon the amplifier, the signal being given a positive polarity to accomplish this.
  • an impulse of negative polarity such as a synchronizing impulse, is impressed upon the amplier.
  • This negative impulse causes a iiow of current through the loop circuit to charge a condenser and control a bias voltage in the amplifier during the succeeding signal period, this flow of current having a magnitude which depends upon any drift that has occurred during the preceding signalperiod.
  • the degenerative loop circuit prevents any appreciable drifting of the amplifier even though it has a very high gain.
  • FIG. 1 is a block diagram of a television system embodying my invention
  • FIG. 2 is a fragmentary view of the scanning disc shown in Figure 1;
  • Fig. 3 is a curve showing thecharacter of the signals impressed upon the main direct-current ampliiier of the transmitter
  • Fig. 4 is a circuit diagram of the apparatus f shown in Figure l;
  • Fig. 5 is a set of curves showing the operation of my improved direct-current amplifier
  • FIG. 6 is a block diagram showing a modification of the transmitter circuit illustrated in Referring to Figure 1, a television transmitter is shown at theleft-hand side of the drawing while a television receiver is shown at the righthand side of the drawing, the transmitter and receiver being connected by a transmission channel as indicated by the dotted lines l and 3.
  • the channel has been exemplified as -conductive merely for purpose of convenience, it being of course understood that my invention is applicable to the ampliiiers utilized in a radio transmitter orradio receiver.
  • the transmitter is shown set up for the transmission of the pictures on a motion picture film Yindicated at 5.
  • the iilm 5 is scanned by means of a scanning disc Iv driven by a motor 9, the scanning disc preferably being ofv the type described and claimed inmy co-pending application Serial No, 544,959, filed June 17, 1931, and assigned to the same assignee as this application.
  • a disc of this type has a ⁇ row of scanning holes ll, and a row of ⁇ synchronizing holes i3 arranged on a circle near the circumference of the disc.
  • Light for scanning the picture is supplied from I e Y a suitable source l5 and passed through an optical system indicated at
  • the photoelectric cell I9 is connected through a battery 2
  • the output circuit of the amplifier 23 isconnected by means of a coupling resistor 25 and inductance coil 21 to the input circuit of the main direct-current amplifier 29 which has a high gain.
  • the coil 21 is employed for improving the high frequency response of the system.
  • the coupling circuit between the ampliers 23 and 29 also includes a condenser 3
  • the output circuit of the amplifier may be connected to the transmission line I-3, as indicated on the drawings, or it may be connected to a radio transmitter for transmitting the picture signal over a radio channel in accordance with well known practice.
  • a balancing network indicated at 33 is provided, its input circuit being connected to the output circuit of the ampliiier 29 and its output circuit, exemplified by the variable resistor shown in dotted lines, being connected across the condenser 3
  • A'suitable light source 35 and optical system 31 are provided for'passing light through the'synchronizing openings I3 in the disc 1 and upon a photo-electric cell 39. ⁇
  • the photo-electric cell 39 is connected through a battery 4
  • the output circuit of the synchronizing amplifier 43 is connected to the input circuit of the directcurrent amplifier 23 through a conductor 45 and a connection which includes a condenser Hand a resistor 49.
  • the synchronizing amplifier 43 is so designed that' ⁇ it supplies synchronizing pulses to the direct-currentampliiier 23 which have a polarity opposite to the polarity of the picture signals, theV scanning disc being provided'with masks so positioned that the synchronizing impulses occur during the intervals that no picture signals are being transmitted.
  • v f The character of the signal applied to the input circuit of the Yamplifier 23 is lshown in Fig. 3. It will be seen that each scanning line of the picture is representedbyvpositive voltage signal waves 5
  • these negative impulses are utilized both for synchronizing the television vapparatus and for controlling the balancing circuit 33 whereby the high gain direct-current *amplier 29 is stabilized, or they may be utilized solely for stabilizing the amplifier.
  • the receiving apparatus shown in Fig. 1 cornprisesa direct-current amplifier 55 which amplies the picture signal and impresses it upon the control grid 51 and cathode 59 of a cathode ray receiving tube 6
  • the cathode ray tube is provided with deflecting lcoils 63 and 65 connected to oscillators indicatedfat 61 and 68, respectively, which provide saw-tooth waves for deflecting the cathode ray beam both ⁇ in a horizontal and in a vertical direction.
  • the deiiecting oscillators 61 and 68 are maintained in synchronism with the transmitting apparatus by means of a synchronizing selector 10 connected to the transmission line
  • a separating circuit 66 is included in the circuit between the selector 69 and the oscillators 61 and 38 for the purpose of separating the horizontal and vertical synchronizing impulses.
  • the directcurrent amplifier 23 comprises an electric discharge tube 1
  • the control grid 15 is maintained at the proper negative bias with respect to the cathode 13 by means of a biasing battery 8
  • the photo-electric cell I9 comprises a cathode 85 and an anode 81, the cathode being connected to the control grid 15 and the anode 81 being connected throughthe battery 2
  • is maintained at the proper positive potential by means of a connection through the plate resistor 25 and coil 21 to the positive terminal of a plate battery 89.
  • the screen grid ⁇ 11 is connected to a suitable point on battery 89.
  • the main direct-current amplifier 29, which has a gain so high that precautions must be taken to avoid drifting, comprises an electric discharge tube 9
  • is connected directly to the anode 19 of the preceding tube 1
  • the cathode 93 is connected to the lower terminal of thecoil 21 through the condenser 3
  • the anode 99 is maintained at avpositive potential bya connection through a plate resistor
  • is connected" directly to the anode 99 of the tube 9
  • 03 is connected to a suitable point on the plate battery
  • is connected through a plate resistor I9 to the positive terminal of a plate battery
  • the balancing circuit comprises an electric discharge tube
  • 21 is connected through ⁇ a biasing battery
  • 25 is connected through a conductor
  • is connected through a plate resistor
  • 23 is connected across the condenser 3
  • 33 is preferably given a value such that the balancer tube
  • the change in bias on the control grid 95 varies gradually with changes in the magnitude of the plate current pulses, these pulses charging up the condenser 3
  • 37 which is effectively in shunt to the condenser, have sufliciently large values to integrate the plate current pulses whereby a bias is applied to ⁇ the input circuit of the high gain amplifier 29 which varies gradually in accordance with any drifting of the amplier.
  • 53 which supplies the synchronizing or control pulses during the intervals of no picture signals, comprises an electric discharge tube
  • 49 is maintained at a suitable bias by means of a connection to the cathode
  • 59 of the photoelectric cell 39 is connected directly to the control grid
  • 53 is connected through a plate resistor
  • the output circuit of the synchronizing amplier 43 is connected to the input circuit of the rst direct-current amplifier 23 by means of the conductors 45 and
  • the direct current amplifier comprises an electric discharge tube
  • is connected through the transmission line conductor to the output circuit of the -direct-current amplier 29 of the transmitter.
  • 79, is connected through the other transmission line conductor 3 to the proper point on the plate battery
  • 77 is connected through a plate resistor
  • is connected through a variable tap to a point on the plate resistor
  • the synchronizing selector 79 comprises an electric ydischarge tube 69 having a cathode
  • 35 are connected to the transmission line conductors and 3 respectively, the cathode connection lincluding a biasing battery
  • is connected through a plate resistor
  • the output circuit of the selector tube 59 is connected to the separating circuit 55 by means of a connection through a couplingv condenser
  • is shown by'the curve in Figure 5.
  • the curve 293 represents the plate current of the balancer tube
  • and 53, respectively, are drawn along a time axis which passes through the value of grid voltage on the abscissa which is equal to the bias voltage on the balancer tube
  • the curves drawn in solid lines represent a condition of the amplifier 29 where there is no tendency to drift.
  • the synchronizing impulses have the proper polarity and magnitude to cause plate current to fiow in the balancer tube each time a synchronizing pulse occurs.
  • These pulses of plate current are represented by the solid line rectangles 205. They are integrated by means of the condenser 3
  • the completeness of balance or the percentage of drifting which is balanced out is proportional to the gain around the closed loop from the balancer control grid
  • the gain around the loop is 10,000 (considering included the effect of having the balancer tube
  • the new equilibrium point is something less than one ten-thousandth volt different on the grid
  • the balance action is then more than 99.99% complete.
  • the highest frequency of noise that may be balanced out is determined by the capacity of the con-denser 3
  • 31 may have values varying within, wide limits. As an example of suitable values, however, a condenser having a capacity of one microfarad and a resistor having a resistance of 100,000 ohms have been found satisfactory.
  • 'Ihe synchronizing impulses are supplied to the input circuit of the balancing amplifier 33 through a conductor 2
  • 9 comprising two electric discharge tubes connected in cascade is provided to prevent the synchronizing impulses which are supplied to the balancer amplifier 33 through the conductor 2
  • the blocking amplifier may consist of an odd number of tubes, but in that case the number of tubes in either the amplifier 29 or in the balancer circuit 33must be changed in order to feed energy from the output of the amplifier 29 to its input in the proper phase to oppose changes in the output current.
  • a separate generator for the synchronizing or balancing impulses may be omitted by giving the picture a steady component of light of such value that the variations due to they picture never modulate the light more than a certain percentage.
  • a picture signal having this character is shown in Figure 7. It will be noted that the picture signal is always above the dotted line axis 22
  • FIG. 8 One form of apparatus for obtaining the type of picture signal shown in Figure 7 is illustrated in Figures 8 and 9, where parts similar to those in Figure 1 are indicated by like reference numerals.
  • the steady component of light is supplied to the photoelectric cell I9 b-y means of a half-silvered mirror 223 positioned between the scanning disc l and the iilm l5. A portion of the light passes through the half-silvered mirror 223, While another portion is reflected to a mirror 225 and, from the mirror 225, to the photoeleotric cell I9.
  • the synchronizing holes are preferably omitted from the scanning disc 'l when employing the half-silvered mirror 223 since they would have no function, the mask 221 being of the proper dimensions to provide a synchronizing interval during which no light passes through the scanning disc.
  • the method of operating a direct-current amplifier for amplifying electrical energy which comprises impressing said energy upon the input circuit of said amplifier periodically whereby there are intervals during which said energy is not being impressed thereon, impressing a voltage impulse during and only during said intervals for controlling a bias voltage in said amplifier.
  • a picture transmitting system including a direct current amplifier
  • the method of transmitting pictures which comprises transmitting picture signals corresponding to scanning lines, transmitting synchronizing signals between scanning lines, impressing saidsignals upon said direct-current amplifier, amplifying said synchronizing signals in accordance with the directcurrent component appearing in the output of said amplifier, and applying a control voltag-e to said amplifier having a value which depends upon said amplified synchronizing signals and having the proper polarity to oppose any change in said direct-current component.
  • a direct-current amplifier having an input circuit and an output circuit
  • a second direct-current amplifier means for so coupling said outp-ut circuit to said input circuit through said second amplifier that a degenerative loop circuit is formed
  • means for impressing signal voltages at one time and control voltages at a different time upon said input circuit and means for permitting only said control voltages to passv through said loop circuit.
  • a direct-current amplifier having an input circuit and an output circuit
  • a second direct-current amplifier means for so coup-ling said output circuit to said input circuit through said second amplifier that a degenerative loop circuit is formed
  • means for impressing signal voltages and control voltages alternately upon said input circuit means for permitting only said control voltages to pass through said loop circuit.
  • second direct-current amplifier means -for so coupling said output circuit to said input circuit through said second amplifier that a degenerative loop circuit is formed, means for impressing signal voltages and control voltages alternately upon said input circuit, means for preventing the circulation of said signal voltages in said loop circuit, and means for controlling a bias voltage in said amplier in accordance with said control voltages.
  • said coupling means includes an electric discharge tube having a bias voltage which varies in accordance with the direct-current component of the output of said amplier.
  • a direct-current amplier having an input circuit and an output circuit, feed-back means for feeding energy from said output circuit toi said input circuit in the proper phase to oppose any change in the output of said amplifier, means for impressing signals upon said input circuit periodically, and means for making said feedback circuit inactive during the periods said signals are being impressed upon said input circuit and for making it active duiing the intervals between said signal periods.
  • Apparatus for amplifying signal voltages comprising a direct-current amplifier having an input circuit and an output circuit, a feed-back circuit coupling said output circuit to said input circuit, said feed-back circuit including an electric discharge tube biased to the region of cut-off and being connected to oppose any change in current in said output circuit, means for impressing said signal voltages periodically upon said input circuit whereby there are intervals of no signal, means for impressing voltage pulses upon said input circuit during said intervals, said pulses having the proper polarity to cause a positive voltage pulse upon, the input electrodes of sai-d electric discharge tube.
  • Electrical apparatus comprising an amplifier having an input circuit, means for impressing signal voltages upon said input circuit periodically whereby there are signal periods separated by intervals of no signal, means for applying a control voltage to said amplier during each of said intervals whereby each control voltage is amplified to a value corresponding to the condition of the amplifier during the interval the said control voltage is applied, means for charging a condenser in accordance with the value of said amplified control voltage, and means for controlling sai-d amplifier in accordance with the charge on said condenser.
  • a direct-current amplifier having an input circuit and an output circuit, means for so coupling said output circuit and said input circuit that a degenerative loop circuit is formed, said coupling means including an electric discharge tube biased beyond cut-off, means for producing signal voltages and control voltages of opposite polarity and for impressing them alternately upon said input circuit, said loop circuit being so designed that said control voltages are of positive polarity when impressed upon said electric discharge tube whereby they are passed through said loop circuit, means responsive to a change in the output of said amplier for changing the bias of sai-d electric discharge tube whereby pulses of control current appear in the output circuit of said tube having values depending upon said change in bias, and means including a condenser shunted by a resistance unit for applying a controlling voltage to said direct-current amplier, said coupling means being connected to charge said condenser in accordance with said pulses of control current.
  • the method of maintaining the amplification factor of a direct-current amplier substantially constant which comprises supplying signals to the amplifier periodically whereby there are intervals during which said signals are not supplied thereto, supplying control signals to the amplifier during said intervals, deriving from the amplied control signals a unidirectional potential and utilizing said potential for controlling the gain in the amplifier.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Picture Signal Circuits (AREA)
  • Transforming Light Signals Into Electric Signals (AREA)
  • Control Of El Displays (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
US718354A 1934-03-31 1934-03-31 Electrical apparatus Expired - Lifetime US2124044A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US718354A US2124044A (en) 1934-03-31 1934-03-31 Electrical apparatus
FR787688D FR787688A (fr) 1934-03-31 1935-03-21 Perfectionnements aux appareils de signalisation électrique
NL73060A NL41139C (enrdf_load_stackoverflow) 1934-03-31 1935-03-30
GB10110/35A GB454511A (en) 1934-03-31 1935-04-01 Improvements in or relating to electron discharge device amplifiers
DE1935R0092992 DE701082C (de) 1934-03-31 1935-04-02 Gleichstromverstaerker, vorzugsweise fuer Fernsehzwecke

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US718354A US2124044A (en) 1934-03-31 1934-03-31 Electrical apparatus

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Publication Number Publication Date
US2124044A true US2124044A (en) 1938-07-19

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Application Number Title Priority Date Filing Date
US718354A Expired - Lifetime US2124044A (en) 1934-03-31 1934-03-31 Electrical apparatus

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US (1) US2124044A (enrdf_load_stackoverflow)
DE (1) DE701082C (enrdf_load_stackoverflow)
FR (1) FR787688A (enrdf_load_stackoverflow)
GB (1) GB454511A (enrdf_load_stackoverflow)
NL (1) NL41139C (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2895006A (en) * 1952-08-28 1959-07-14 Eastman Kodak Co Apparatus for balancing scanning systems

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE752761C (de) * 1935-11-02 1954-02-08 Telefunken Gmbh Verfahren zur Schwundregelung der Ausgangsamplitude des Verstaerkers fuer den Empfang von Fernsehsendungen

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2895006A (en) * 1952-08-28 1959-07-14 Eastman Kodak Co Apparatus for balancing scanning systems

Also Published As

Publication number Publication date
GB454511A (en) 1936-10-01
DE701082C (de) 1941-01-08
FR787688A (fr) 1935-09-26
NL41139C (enrdf_load_stackoverflow) 1937-07-15

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