US2226230A - Signaling circuit - Google Patents

Description

Dm. 24, 1940. A. A. LINSELL ,23

SIGNALING CIRCUIT Filed Nov. 27, 1936 2 Sheets-Sheet l Eig- 1 INVENTOR ALFRED A. L/l/J'EU.

DATII'ORNEYH Dec. 24, 1940.

SIGNALING CIRCUIT Filed Nov. 27, 1936 2 Sheets-Sheet 2 Fig 8 INVENTOR- ALFRED A. L/MSELL BY/ I ATTORNEY A. A. LKNSELL 2,226,230

Patented Dec. 24, 1940- SIGNALING CIRCUIT Alfred Aubyn Linsell, Sydenham, London, 'Eng- ,land,'assignor to Radio Corporation of America,

a corporation of Delaware Application November 27, 1936, Serial No. 113,026

-In Great Britain December 3, 1935 4 Claims.

This invention relates to television receivers and .has for its object to provide an improved receiver capable of reproducing television pic.- .tures transmitted from different transmitters 5 operating with different scanning line frequencies. This application is a continuationin'part of applicants copending application entitled Television receivers which was filed November 27, 1936, and whose Serial No. is 113,025.

According to this invention a television receiver capable of reproducing difierent television programmes transmitted with predetermined different scanning line frequencies comprises manually operable adjustment selecting means for :5 selecting among a number of predetermined adjustment settings providedin said receiver (in manufacturing the same) so that for each of a plurality of positions of said selecting means one of said predetermined settings appropriate for,

receiving one television programme is selected said receiver comprising also means automaticallyv and selectively operated under the control 'of'the' scanning line frequency in the television signals being received at any time for giving an indication as to which one of the plurality of possible positions of the manual selecting means should be adopted to adjust said receiver to receive the incoming programme. In place of or as well as employing indicator means automatically' and selectively operated under scanning line'frequency control there may be employed similarly operated means for limiting the freedom of movement of the manual selecting means so as to prevent movement thereof into a position which should be adopted to adjust said receiver to receive a programme other than the incoming programme.

The invention is illustrated in and further explained in connection with the accompanying diagrammatic drawings in whichFig. 1 shows schematicallya circuit illustrative of the simultaneous selection of scanning frequency and spot size; Fig. 2 shows schematically one embodiment of applicants invention showing lamps for indieating selected combinations of spot size and scanning frequency; Fig.3 shows a modification of applicants invention shown in Fig. 2; and Figs. 4 through9 are illustrations of selecting means useful for explaining the operation of applicants invention.

Although a number of circuit adjustments maybe necessary when changing over a cathode ray tube television receiver froma state in which ;i1;- can reproduce pictures transmitted with one scanning line frequency to a state in which it can reproduce pictures transmitted with another, there will be in general two main adjustments, the first an adjustment as to scanning line frequency and the second an adjustment as 5 to scanning spot. size. Consider a normal case (see Figure 1) where a cathode ray reproducer tube I is provided with a cathode 2 a control electrode 3 and two apertur ed tubular auxiliary anodes 4, 5, in succession in the path of the elec- '10 tron beam, that which is further from the cathode 2 (namely anode 5) receiving 'a higher bias potential than the other. In general the bias potentials for the two auxiliary anodes are ob-.

tained-as shown in Figure 1 fromthe same source 15 6 of potential, the lead to the lower potential anode 4 being connected to a tap upon the source. The size of the spot produced by the cathode rayupon the fluorescent screen of the tube will be a function of the relative potential between 2120 the two auxiliary anodes 4, 5, and accordingly .one change in adjustment which may be made .when changing over from reception withone scanning line frequency to reception with another-a change over which involves a -change325 in spot sizeis a change in the potential or potentials applied to one or both the auxiliary anodes. In carrying out the present invention in the embodiment shown in Fig. 1 the higher potential auxiliary anode '5 is connected to the 3 positive terminal .ofthe potential source 6 and the lower potential anode 4 is connected to a switch 1, which is manually operated in manner to be described later, which can contact as .shown with either of two different taps upon the said potential source. The taps are such that for one position of the :switch thespot size vis correct for reception of pictures having one (predetermined) scanning line frequencywhile for the other switch position the spot size is correctfor reception of pictures having the other (predetermined) scanning line frequency.

As regards the question of adjustment :of the scanning line deflecting frequency at ,the receiver, assume that this deflection is obtained electrostatically by mutually perpendicular pairs ,of plates 9, III, as in the usual way by saw-tooth waves derived from'a synchronized saw-tooth wave generator such as a relaxation oscillator generator or blocking oscillator generator-rep-y resented in Figure 1 by a rectangle 8-whose operating frequency is determined by therate ,of charge (or in some cases of discharge) of a condenser associated with aresistance. 'GbVi- 'ously if a single frequency determining condenserg,

be provided and there be two resistances of different value adapted to be selectively connected in circuit by means of a suitable switch, then two deflecting line frequencies may be obtained according as to which resistance is in circuit. Therefore, in carrying out the present invention in the embodiment shown in Figure 1 there is provided a switch [4, mechanically or otherwise uni-controlled with the switch 1 so as to be manually controlled therewith, connected so that it selects either of two resistances l2 or l3 for connection with the frequency determining condenser Il so that either of two scanning line frequencies can be obtained from the generator. As stated the switches I 4 and I are uni-controlled (the mechanical interconnection is indicated by a chain line) so that the frequency and scanning spot size selected for one position of the switches are appropriate for giving scanning action at one of the desired scanning line frequencies and those selected for the other position are appropriate for giving scanning action at the other.

The accompanying Figure 2 shows diagrammatically an indicator arrangement, automatically operated under the control of the scanning line frequency in incoming television signals, for indicatingtheposition into which the adjustment selecting means (the switches 1 and I4 of Fig. 1) should be moved to receive the said signals.

Referring to Fig. 2 the demodulated or television signal output from the radio receiver proper represented by the rectangle I5 of Fig. 2 of the whole receiving apparatus, passes to two auxiliary circuits IE, I7, one of which is tuned to one and the other to the other of two predetermined scan line frequencies for which the receiving apparatus is adapted. Of course if the receiver is to be able to receive on more than two scan line frequencies, there will be a correspondingly increased number of tuned circuits, a correspondingly increased number of tuned circuits, a correspondingly increased number of possible predetermined adjustments and a correspondingly increased number of switch positions,one for each adjustment. In order to improve the sharpness or selectivity of these tuned circuits tuning forks or equivalent mechanically resonant devices may be employed as indicated at I8, l9. These resonant circuits l6, [1, feed into rectifiers 20, 2|, in circuit with the operating windings of relays 30, 3 I, which are thus actuated by the rectified currents. The relays control pilot or indicator lamps 32 or 33 as shown. Obviously such further amplification as may be desired may be provided e. g. amplifying valves could be interposed between the rectifier circuits and the relays 30, 3| while obviously also indicators and relays of forms other than those shown in Fig. 2 could be employed.

The accompanying Fig. 3 shows schematically another embodiment of the invention while the accompanying Figs. 4 and 5 shown in two possible positions the switch control device SW of Fig. 1 the accompanying Fig. 6 showing, in an intermediate position, a slightly modified and preferred control device SW.

In Fig. 3 the rectified resultant from the tuned circuits l6, l1, and rectifiers 2|], 2| (the selectivity of the former may be increased, as in Fig. 1, by means of tuning forks) are fed as shown to the operating windings 34, 35 of a differential voltmeter or galvanometer 35 which is mounted, e. g. on the panel of the television receiver, in close proximity (e. g. just above) a switch control device SW having an operating arm SWI terminating in a knob SW2. This device is so arranged that the arm SWI can be pulled forward from a position as shown in Fig. 4 into a position as shown in Fig. 5 after which it may be moved either to the right or the left. This limited freedom of movement is secured by the T-shaped slot SW3. The device SW controls suitable switches (not shown) so that in the position of Figure 4 the receiver is switched off. By pulling the arm SW'L forward into the position of Figure 5 all the receiver cir cuits are made except that for the normally provided saw-tooth scanning wave generator means (not shown) and the anode circuit of the reproducer cathode ray tube. (This tube is only schematically illustrated in Fig. 3). By moving the knob SW2 to the left the scanning wave generator circuit is completed to cause it to produce one of the predetermined scan line frequencies and the tube anode circuit is completed in such manner as to result in a scanning spot of the appropriate size for that frequency. By moving the knob SW2 to the right, the other scanning line frequency and spot size are obtained. The actual switches controlled are not shown in Fig. 3 but those operated by right and left movements of the knob SW2 across the head of the T-slot SW3 are, of course, switches corresponding as to function with the switches 1, I4, of Fig. 1. The

arrangement of the meter 36 relative to the de- 5 vice SW is preferably such that when the needle 31 of the meter is deflected to the left, the knob SW2 should be moved to the left and when the needle moves to the right the knob SW2 should be moved to the right. Preferably also a spring SW4 is provided in association with the arm SWI as shown in Fig. 6 so that the said arm will return automatically to the off position unless the knob SW2 be moved to one or other of the operative positions in the head of the T-slot SW3.

The provision of this spring ensures that the operator does not leave the switches in such positions that the television apparatus is in operation (except for scanning action) to give a stationary spot which might burn or overheat the fluorescent screen of the tube.

In a further modification, instead of using a meter 36 indicator lamps, such as the lamps 32, 33, in an arrangement as illustrated in Figure 2 are provided at opposite ends of the head of the T-slot SW3 so that when the lamp 32 lights it indicates that the knob SW2 should be moved towards it and when the lamp 33 lights the contrary indication is given. This arrangement of lamps and switch control device is represented in the accompanying Figure 7.

The accompanying Figure 8 shows another arrangement employing lamps 32, 33, and aswitch control device SW but here the lamps 32, 33, are employed in manner different from that in Figure 1. In Figure 8 both lamps are lit when the arm SWI is moved forward into the head of the T-slot SW3 irrespective of the position of the said arm in that slot head. Between each lamp and an observer is a tuning fork 38 or 39 one responsive to one scanning line frequency and the other to the other. The tines of each fork carry oppositely disposed masks 38a, 38b or 39a, 3917 with slots 38c, 38d or 39c, 39d cut therein. These masks are so arranged that when a fork is stationary the slots in the masks carried thereby are out of alignment and the masks conceal the appropriate lamp 32 or 33 from an observer. When a fork vibrates the slots in the masks carried thereby cross during vibration and accordingly 75 the .lamp behind-them can be seen. The forks are adapted to be vibrated "by a coil or coils (not shown) fed withthe incoming scanninglin'e frequeney and it will be seen-that only one fork (whose frequency is'the same asthe sc'anning line frequency) will vibrate. If desired, and preferably, in order to economise current, the device'SW maybe arranged to sw itch out the lamp circuits not only, when in the on position (as shown in F;igure'-4) 'but when itis moved to either end'of the head 'of the T-slot SW3.

, ing programme. The member 40 may be moved automatically in anyconvenient way in dependence upon the incoming scanning line frequency; for example, as indicated, the ends 40a 40b may constitute the armatures of two magnet coils 42,

I 43, energized in the same way as the relay windings 30, 3! of Figure 2.

, Having now described the invention what is I claimed is:

1.--In a television system wherein a cathode ray tube is provided for producing an electro-optical image representation upon a luminescent target area of the tube, the method of producing images which includes the steps of selectively receiving television signals of difierent character to represent image transmissions of a subject scanned in different degrees of detail and at coordinated repetition rates, developing a cathode ray beam within the tube, controlling the intensity of the cathode ray beam under the control of the received signals, developing electrical energy to cause the produced beam to scan the tube target while maintaining the target area scanned subaccording to predetermined repetition rates and patterns selectively separate one from the other, developing electrical energy to focus the cathode ray beam upon'the target in selectively obtainable and separable cross-sectional areas, coordinating different scanning repetition rates and patterns with different beam cross-sectional areas at the target so that for each selected combination the scanned area of the tube target remains substantially constant, deriving directly from the'received signals an indicationof the scanning detail and pattern of the instantaneously received signals independent of the pro- 2, A television receiver comprising a cathode ray tube having a luminescent target element whereon electro-optical replicas of images are caused to appear for observation, means within the cathode ray tube for developing and focusing the images, a beam intensity control means associated with the said tube, a plurality of means each adapted'to cause the developed beam to scan the target according to a predetermined pattern of scanning, switching means to change the pattern of scanning for each position of the switching means from one scanning rate to another stantially constant for each scanning, a second switching means cooperatively associated with ent' cross-sectional areasof the beam as it strikes the said tube target, the said switching means being interlocked-so that a predetermined relationship exists between different scanning-rates and-the beam cross-sectional areas at impact pictures and different scanning details and scanning rates, meansto control the intensity-of the beam by the received signals, and means respon- "sive 'to the received signals for'producing, independently of the scanning operation,- an indication directly therefrom of the scanning detail and scanning rate at which the signals receivedwere initially developed so that selection of different cross-sectional beam areas at the target and different scanning rates may becobtained by operation of the said switching means and so that the image reproduction upon the tube target may be directly coordinated with the transmitted signals.

3. A television receiver comprising a cathode ray tube having a luminescent target element whereon electro-optical replicas of images are caused to appear for observation, means within the'first switching means-for-varying in each position thereof-the beam focus to produce differupon the target," means to receive signalsof differing character to represent'different scanned the cathode ray tube for developing and focusing an electron beam upon the tube target to produce luminous effects by impact, a beam intensity control means associated with the said tube, a plurality of means for controlling the deflection of the developed beam so as to cause it to scan-the target according to a predetermined pattern-of scanning for each of the plurality of control means, a multiple contact switching means associated with the beam deflection control means to change the pattern of scanning for each contact position of the switching means from onescandifferent'scanned pictures and different scanning details and scanning rates, and means responsive to the received signals and operating independently of the electro-optical image production for producing an indication of thescanning detail I and scanning rate at which the signals were initially developed so that selection of different cross-sectional beam areas at the target and different scanning rates may be obtained by operation of the said switching means andso that the image reproduction upon the tube target may be directly coordinated with the signals actually received.

4. A television receiver comprising a cathode ray tube having a luminescent target element whereon electro-optical replicas of images are caused to appear for observation, means within the cathode ray tube for developing an electron beam, means for focusing the said beam upon the said target so that the area of instantaneous beam impact is of predetermined cross-section, means for receiving picture and synchronizing signals, means for controlling the intensity of the luminous electro-optical effects under the control of the signals received, means for causing the developed beam to scan the target according to a predetermined pattern of scanning, switching means to change the pattern of scanning for each position of the switching means from one scanning rate to another while maintaining the target area scanned substantially constant for each scanning, a second switching means for varying the beam focus in each position thereof so that the cross-sectional area of the beam as it strikes the said tube target may be varied, means for interlocking the said switching means so as to establish a predetermined relationship of scanning rates and beam cross-sectional areas at impact, and electronic means responsive to the received signals for producing therefrom separately from the image reproduction an optical indication of the scanning detail and scanning rate at which 5 the signals were initially developed so that different cross-sectional beam areas at the target and difierent scanning rates may be obtained by operation of the said switching means and so that the image reproduction upon the tube target may 10 be directly coordinated with the signals actually received.

ALFRED AUBY'N LINSELL.

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