US2049629A - Television receiving apparatus - Google Patents

Description

'Aug4, 1936.-

G. SCHUBERT 'TELEVISION -REcEggv1NG APPARATUS Filed April 20, 1932 Patented ug. 4, 11.936

UNITED STATES I TELEVISION RECEIVING Georg Schubert, Berlin, Germany, assigner to the firm Fcrnsh Aktien-Gesellschaft, Zehlendorf,

near Berlin, Germany Application April 20, 1932, Serial No. 606,471 In Germany April 24, 1931 4 claims. (ol. 17a-s) In television practice the sources of light usually employed for giving a luminous'surface are the known surface glow'discharge lamps. The

ordinary surface glow discharge lamp has the 5 advantage that it can be controlled with simple means and without particular expenditure, but in the case of high image point numbers it provides relatively faint television pictures.

'1t hasm fact already been proposed to en.

l0. ploy the positive column of gas discharges, but heretofore, in order tobe freefrom disturbances, they have been operated with modulated high frequency,` exceedingly high voltages being required for this purpose. Moreover it has not been possible to eliminate these disadvantages even by employing oxide cathodes. Heretofore, for the. operation of luminous tubes it has always been necessary to employ a high-frequency transmitting valve with low frequency modula- In contradistinction to the previous compli cated methods of operating with high frequency, the present invention consists in operating the luminous tube with continuous voltage and in connecting it.directly in series with the output valve of the low-frequency amplifier, so that the anode .current ofthe output valve, for example an R E 604, vflows through the luminous tube. In contradistinction to any other method of I0 coupling, auch as chokes, transformers, etc., this circuit connection has the additional advantage of working perfectly independently of the frequency. It is immaterial whether the luminous tube is provided with a. heated cathodeor not,

85 and likewise, the cathode may be heated by 'direct current or alternating current.

Certain difficulties arise, however, in operating the positive-column luminous tube with continuous voltage. The luminous tube is'readily 40 extinguished at the moment modulation begins, and with modulation of varying strength it works so irregularlyy as to be unsuitable forsatisfactory reproduction. As mentioned hereinbefore this unreliable working has also'rcsulted 45 in the fact that heretofore luminous tubes -were never operated with continuous voltage but always with high-frequency, because the dimculties do not then occur. According to a feature of the present inven- 50 tion, all the aforementioned difficulties in the operation of luminous tubes with continuous voltage may .be obviated by exciting the luminous tube with high frequency. Very small outputs are sufficient for this, and quite ordinary broadcasting valves, for example an R. E 134 or weaker valves, will suiiice'.l The coupling of the Y high frequency is preferably effected capacitatively and, since very small'capacities are suilicient for coupling, this may be done by simply placing behind the luminous tubes a metal plate o to which is connected a lead from the highfrequency circuit. The other lead is preferably connected directly to the cathode. At the same time, the metal plate used for capacity coupling may also be constructed in the form of a me- 1o tallic mirror, in which case it will increase the uniformity of the luminosity of the image surface.

The accompanying drawing shows the complete circuit of a luminous tube fortelevision 16 purposes,the said tube being, according to the invention, operated with continuous voltage and excited with high frequency. In the drawing, the output valve of the low frequency amplifier 'is shown at I, 2 is the luminous tube connected 20 in series therewith, 3 is the oscillating valve for generating the high frequency and 4 is the metal plate or metallic mirror which is used for the capacity coupling of the luminous tube to the high-frequency circuit. A resistance 5 bridged 25 by a capacity 6 is used for regulating the current intensity of the luminous tube. All the remaining details will be gathered without diillculty from the circuit diagram itself.

' Having now particularly described and ascer- 30 tained the nature of my said invention and in whatV manner the same is to be performed, I declare that what I claim is:-

l. In a television system, the combination of a low-frequency amplifier having an outputvvalve, a variable resistance and a positive-column luminous tube having a` descending current voltage characteristics and having its electrodes spaced longitudinally of the tube connected in series with said resistance in the anode circuit `of said output valve, a condenser is shunt to said resistance, and means for continuously capacitatively exciting said luminous tube with high frequency.

2. The combination in a television system, of a low frequency amplifier having an output valve, a positive-column luminous tube and means for continuously capacitatively exciting said luminous tube with high frequency, means for connecting said positive-column luminous tube iq the anodecircuit of said output tube including a variable resistance arranged in a lead connecting one electrode of said luminous tube with the anode of said output tube, and a condenser shuntedacrossgsaid iesistan :e., v 55 3. The combination in a television system, of a low frequency amplifier having an output valve, a positive-column luminous tube and meansy for continuously capacitatively exciting said luminous tube with high frequency, means for connecting said positive-column luminous tube in the anode circuit of said output tube including a variable resistance arranged in a lead connecting one electrode of. said luminous tube with the anode of said output tube, and a condenser in shunt to said resistance, said means for capacitatively exciting said luminous tube with high frequency including .a high frequency circuit, an oscillating valve for generating high frequency in said high frequency circuit, and a metallic plate connected with said last named circuit and arranged behind said luminous tube for establishing a capacitative coupling between said high frequency circuit and said luminous tube. i

4. The combination in a television system, of

a low frequency amplifier having an output valve, a positive-column luminous tube and means for continuously capacitatively exciting said luminous tube with high frequency, means for connecting said positive-column luminous tube in the anode circuit of said output tube including a variable resistance arranged in a lead connecting one electrode of said luminous tube with the anode of said output tube, and a condenser in shunt to said resistance, said means for continuously capacitatively exciting said luminous tube with high frequency comprising an independent high frequency circuit, an oscillating valve for generating high frequency in said highy frequency circuit, and a metallic plate having a reflecting surface connected with said last named circuit and arranged behind said luminous tube for establishing a capacitative coupling between said high frequency circuit and said luminous tube.

GEORG SCHUBERT.

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