GB1176462A - Improvements in or relating to Levelling Circuits - Google Patents

Improvements in or relating to Levelling Circuits

Info

Publication number
GB1176462A
GB1176462A GB179666A GB179666A GB1176462A GB 1176462 A GB1176462 A GB 1176462A GB 179666 A GB179666 A GB 179666A GB 179666 A GB179666 A GB 179666A GB 1176462 A GB1176462 A GB 1176462A
Authority
GB
United Kingdom
Prior art keywords
signal
resistor
constant
circuit
clamp
Prior art date
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
Application number
GB179666A
Inventor
Griffith John Raymond Chanot
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.)
EMI Ltd
Electrical and Musical Industries Ltd
Original Assignee
EMI Ltd
Electrical and Musical Industries Ltd
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 EMI Ltd, Electrical and Musical Industries Ltd filed Critical EMI Ltd
Priority to GB179666A priority Critical patent/GB1176462A/en
Publication of GB1176462A publication Critical patent/GB1176462A/en
Expired legal-status Critical Current

Links

Classifications

    • 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
    • H04N5/18—Circuitry for reinsertion of dc and slowly varying components of signal; Circuitry for preservation of black or white level by means of "clamp" circuit operated by switching circuit
    • H04N5/185—Circuitry for reinsertion of dc and slowly varying components of signal; Circuitry for preservation of black or white level by means of "clamp" circuit operated by switching circuit for the black level
    • 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
    • H04N5/18—Circuitry for reinsertion of dc and slowly varying components of signal; Circuitry for preservation of black or white level by means of "clamp" circuit operated by switching circuit

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Picture Signal Circuits (AREA)

Abstract

1,176,462. Picture signal circuits; semiconductor circuits. ELECTRIC & MUSICAL INDUSTRIES Ltd. 16 Jan., 1967 [14 Jan., 1966], No. 1796/66. Headings H4F and H3T] A television signal is coupled from an input terminal 1 to an output terminal 3 by way of a main high-pass filter channel comprising a capacitor 2 and a resistor 7, a unity gain feedback path being provided from the output terminal 3 to the lower end of resistor 7 through a circuit comprising unity gain amplifiers 4 and 6 and a clamp circuit 9 which operates in response to pulses occurring during the line back-porch intervals to connect the lower end of resistor 8 to a reference potential 11. The time-constant of the RC combination 2, 7 is substantially larger than the time-constant of the RC combination 5, 8; ten times in the particular embodiment described. At frequencies at and above line frequency the feedback path causes resistor 7 to behave effectively as a very high value resistor, whereby the signal is transmitted with negligible loss or distortion. At frequencies below line frequency the clamp 9 causes the signal at the lower end of resistor 7 to differ from that at the top if there is any error in the signal lever. The effective time-constant of capacitor 2 and resistor 7 is thereby reduced, causing attenuation of the signal and a reduction in the error. The circuit is of use with a colour television signal since it permits signal level control without loss of the colour synchronizing " burst " which occurs during the back porch interval. With monochrome signals, where there is no back porch signal to be disturbed by the clamp operation, an output signal of improved signalto-noise ratio may be taken.
GB179666A 1966-01-14 1966-01-14 Improvements in or relating to Levelling Circuits Expired GB1176462A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB179666A GB1176462A (en) 1966-01-14 1966-01-14 Improvements in or relating to Levelling Circuits

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB179666A GB1176462A (en) 1966-01-14 1966-01-14 Improvements in or relating to Levelling Circuits

Publications (1)

Publication Number Publication Date
GB1176462A true GB1176462A (en) 1970-01-01

Family

ID=9728167

Family Applications (1)

Application Number Title Priority Date Filing Date
GB179666A Expired GB1176462A (en) 1966-01-14 1966-01-14 Improvements in or relating to Levelling Circuits

Country Status (1)

Country Link
GB (1) GB1176462A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0120586A2 (en) * 1983-02-25 1984-10-03 Sony Corporation Signal processing circuits

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0120586A2 (en) * 1983-02-25 1984-10-03 Sony Corporation Signal processing circuits
EP0120586A3 (en) * 1983-02-25 1987-09-16 Sony Corporation Signal processing circuits

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