GB649724A - Improvements in or relating to photo-electric circuits - Google Patents

Abstract

649,724. Television. PHILIPS ELECTRICAL, Ltd. Nov. 24, 1947, No. 31045. Convention date, Nov. 27, 1946. [Class 40 (iii)] [Also in Group XL (c)] The capacity change between the signal plate 5 (Fig. 1) and the electron collecting electrode 6 of an iconoscope type tube which results when an optical image on the mosaic 3 is scanned by an electron beam, is employed to vary the frequency of an oscillator 12 from which frequency modulated television signals are obtained for transmission. In a further arrangement (Fig. 2) a frequency modulated output signal derived from oscillator 19 is connected to an amplitude modulated signal in a frequency discriminator 24 and combined, in potentiometer 21, with an amplitude modulated signal produced across a conventional signal plate load resistor 14, a series resonant circuit 15, 16 tuned to the oscillator frequency and connected in parallel with resistor 14 preventing oscillatory voltages of the oscillator frequency from being set up across this resistor. This combined signal may be applied either to a television transmitter or, through an amplifier 26, to a monitoring tube 27. It is stated that distortions which normally occur in image transmission may be eliminated by the last arrangement since the distortions in the two derived signals are of a different nature and may be made to cancel one another. In a further embodiment a photo-electric cell is employed as the frequency modulating device and the derived signals are applied to a monitoring or local viewing tube (Fig. 3, not shown).