726,134. Non-linear valve circuits. STANDARD TELEPHONES & CABLES, Ltd. June 5, 1953 [July 26, 1952], No. 15567/53. Class 40 (6). In a gamma correction circuit as used in a television system, correction is effected in the lower and middle frequencies and frequency compensation effected at the higher frequencies. A negative-going sawtooth 9 from a pick-up device 10, Fig. 5, D.C. restored by valve 8, is applied over cathode follower 7 to an attenuator comprising resistor 4 and a germanium diode 1 which is biased by the voltage drop over resistors 14, 15 to give an output waveform 12. At the higher frequencies, capacitor 5 reduces the attenuation caused by resistor 4. The gamma of the circuit may be changed by varying resistors 15, 4.
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