Patent US3429337A successfully refreshed from Google Patents.
Patent EP0074081A2 successfully refreshed from Google Patents.
EP0074081A2
Expired / Lapsed
EP
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Signal processing unit
Assignee: NEC Corp
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Filing: 1982-09-01
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Granted: —
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Expires: 2002-09-01
Abstract
Abstract A signal processing circuit in a television system for alternatively outputting one of two input video signals, for example a normal video signal and an additional teletext or similar signal, is disclosed. Before the two signals are applied to a signal switching means, their pedestal potentials are equalized by clamping the pedestal potential of one signal to a reference voltage and comparing the pedestal potential of the other signal with said reference voltage and using the comparison signal for a feedback control of said other signal. Also the maximum amplitude levels of the two signals may be equalized by feeding one of the signals through an attenuator having a suitable attenuation factor and having a control input supplied with said reference voltage for attenuating only the A.C. component of said one signal.
Inventors
- 👤 Masaki C/O Nippon Electric Co. Ltd. Ikeda
- 👤 Tatsuyuki C/O Nippon Electric Co. Ltd Amano
- 👤 Kazuo C/O Nippon Electric Co. Ltd. Tokuda
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 13:39
CPC Classifications
H; H04; H04N; H04N9/00; H04N9/64; H04N9/641
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
89 words
A signal processing circuit comprising switching means adapted to receive a first signal for a first image and a second signal for a second image for outputting either one of said first and second signals, clamping means for clamping a pedestal potential of said second signal at a reference voltage, comparator means for comparing a pedestal potential of said first signal with said reference voltage, and feedback means responsive to the output of said comparator means for equalizing the pedestal potential of said first signal to said reference voltage.
Claim 2
Dependent Claim
89 words
A signal processing circuit comprising switching means adapted to receive a first signal for a first image and a second signal for a second image for outputting either one of said first and second signals, clamping means for clamping a pedestal potential of said second signal at a reference voltage, comparator means for comparing a pedestal potential of said first signal with said reference voltage, and feedback means responsive to the output of said comparator means for equalizing the pedestal potential of said first signal to said reference voltage.
Claim 3
Dependent Claim
26 words
A signal processing circuit as claimed in Claim 1, further comprising attenuator means inserted in the input path of said first signal to said switching means.
Claim 4
Dependent Claim
74 words
A signal processing circuit as claimed in Claim 2, in which said attenuator means has input, output and common ends, said first signal being applied to said input end, said output end being coupled to said switching means, said reference voltage being applied to said common end, and the attenuation factor of said attenuator means being preset such that the maximum amplitude levels of said first and second signals are equalized to each other.
Claim 5
Dependent Claim
195 words
A combination suitable for a television receiver, comprising, first signal processing means for generating at least one first signal having a first D. C. level, first clamping means for clamping said first D. C. level of said first signal to a first voltage, second signal processing means for generating at least one second signal having a second D. C. level, generating means for generating a second voltage, second clamping means for clamping said second D. C. level of said second signal to said second voltage, comparing means for comparing said first D. C. level with said reference voltage, producing means responsive to an output of said comparing means for producing a third voltage, said third voltage being varied by said output of said comparing means, supplying means for supplying a voltage proportional to said third voltage to said first clamping means as said second voltage, receiving means for receiving said first signal having the first D. C. level clamped to said first voltage and said second signal having the second D. C. level clamped to said second voltage, and output means coupled to said receiving means for outputting one of said first and second signals.
Claim 6
Dependent Claim
195 words
A combination suitable for a television receiver, comprising, first signal processing means for generating at least one first signal having a first D. C. level, first clamping means for clamping said first D. C. level of said first signal to a first voltage, second signal processing means for generating at least one second signal having a second D. C. level, generating means for generating a second voltage, second clamping means for clamping said second D. C. level of said second signal to said second voltage, comparing means for comparing said first D. C. level with said reference voltage, producing means responsive to an output of said comparing means for producing a third voltage, said third voltage being varied by said output of said comparing means, supplying means for supplying a voltage proportional to said third voltage to said first clamping means as said second voltage, receiving means for receiving said first signal having the first D. C. level clamped to said first voltage and said second signal having the second D. C. level clamped to said second voltage, and output means coupled to said receiving means for outputting one of said first and second signals.
Claim 7
Dependent Claim
41 words
A combination as claimed in claim 4, wherein said producing means has a capacitor, charge and discharge currents of said capacity being controlled by said output of said comparing means, a voltage across said capacitor being utilized as said third voltage.
Claim 8
Dependent Claim
40 words
A combination as claimed in claim 4, wherein said receiving means has first and second transistor amplifiers whose gains are substantially identical, and said output means has first and second differential amplifiers coupled to said first and second transistor amplifiers.
Claim 9
Dependent Claim
26 words
A combination as claimed in claim 4, further comprising attenuating means for said first signal, said receiving means receiving said first signal through said attenuation means.
Claim 10
Dependent Claim
172 words
A signal processor comprising a first input terminal supplied with a first color signal, a second input terminal supplied with a second color signal, a reference voltage generator generating a reference voltage, a clamp circuit clamping a pedestal level of said second color signal to said reference voltage, a comparator comparing a pedestal level of said first color signal with said reference voltage and generating an output corresponding to a voltage difference between the pedestal level of said first color signal and said reference voltage in order to equalize the pedestal level of said first color signal to said reference voltage, a switching control terminal, and a switching circuit coupled to said switching control terminal and having first and second input ends respectively supplied with said first and second color signals whose pedestal levels are equal with each other and an output and, said switching circuit supplying one of said first and second color signals to the output end thereof in response to a control signal supplied to said switching control terminal.
Claim 11
Dependent Claim
172 words
A signal processor comprising a first input terminal supplied with a first color signal, a second input terminal supplied with a second color signal, a reference voltage generator generating a reference voltage, a clamp circuit clamping a pedestal level of said second color signal to said reference voltage, a comparator comparing a pedestal level of said first color signal with said reference voltage and generating an output corresponding to a voltage difference between the pedestal level of said first color signal and said reference voltage in order to equalize the pedestal level of said first color signal to said reference voltage, a switching control terminal, and a switching circuit coupled to said switching control terminal and having first and second input ends respectively supplied with said first and second color signals whose pedestal levels are equal with each other and an output and, said switching circuit supplying one of said first and second color signals to the output end thereof in response to a control signal supplied to said switching control terminal.
Claim 12
Dependent Claim
87 words
A signal processor as claimed in claim 8, further comprising an attenuator having input, output and common ends, said input end of said attenuator being connected to said first input terminal, said output end of said attenuator being connected to said first input end of said switching circuit, said common end of said attenuator being supplied with said reference voltage, and said attenuator having such an attenuation factor that the maximum amplitude level of said first color signal become equal to that of said second color signal.
Claim 13
Dependent Claim
136 words
A signal processor as claimed in claim 8 or 9, wherein said switching circuit has first and second transistors of a common-emitter type, third and fourth transistors constituting a first differential amplifier, and fifth and sixth transistors constituting a second differential amplifier, bases of said first and second transistors being connected to said first and second input ends of said switching circuit, collectors of said first and second transistors being coupled to said first and second differential amplifiers, said third and sixth transistors being turned on in response to a first level of said control signal, said fourth and fifth transistors being turned on in response to a second level of said control ' signal, and a signal through said fourth transistor or said sixth transistor being supplied to said output end of said switching circuit.
Claim 14
Dependent Claim
54 words
A signal processor as claimed in claim 10, further comprising a gate pulse input terminal receiving a gate pulse, said comparator having a seventh transistor receiving said gate pulse from said gate pulse input terminal, and eighth and ninth transistors receiving said pedestal level of said first color signal and said reference voltage, respectively.
References Cited (Backward Citations)
No citation records indexed.
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