Selectively operated tint correction circuit

Claim 2

Apparatus for shifting the phase of an A.C. signal applied to an input terminal of a signal processing circuit while simultaneously reducing the amplitude at the output terminal of said processing circuit, comprising, a. an active device having an input, output and common electrodes, said common electrode being coupled to a point of reference potential, b. first means coupling the output electrode of said active device to said output terminal of said processing circuit, c. rectifying means including a first capacitor in series therewith coupled between said input terminal of said processing circuit and a point of reference potential, said rectifying means being poled to conduct only for certain polarity excursions of said A.C. signal applied to said input terminal of said processing circuit to develop a D.C. level across said capacitor, d. second means coupling said capacitor to said input electrode of said active device to render the same nonconducting in accordance with said D.C. level, e. switching means coupled to said second means, said switching means operative in a first mode to forward bias said rectifying means and said active device to cause said rectifying means to alter the phase of said A.C. signals at said input terminal of said processing circuit and said first means to reduce the amplitude at said output of said signal processing circuit in accordance with the forwaRd biasing of said active device.

Claim 3

The apparatus according to claim 1, wherein said active device comprises a transistor having an input base electrode, a common emitter electrode and an output collector electrode.

Claim 4

The apparatus according to claim 1, wherein said first means coupling the output electrode of said active device to said output terminal of said processing circuit comprises a first resistive impedance.

Claim 5

The apparatus according to claim 1, wherein said processing circuit is a color demodulator configuration and said A.C. signal is the color reference subcarrier signal.

Claim 6

The apparatus according to claim 3 wherein said second means coupling said capacitor to said input electrode of said active device is a second resistive impedance.

Claim 7

The apparatus according to claim 1, wherein said rectifying means includes a third resistor and second a capacitor connected in parallel therewith to form an R.C. network, which network is coupled in series between said input terminal of said processing circuit and said rectifying means and said first capacitor in the order named.

Claim 8

Apparatus for shifting the phase of a reference signal applied to one input terminal of a demodulator while simultaneously reducing the amplitude at the output terminal of said demodulator, comprising, a. a transistor having a base, collector and emitter electrode, said emitter electrode being coupled to a point of reference potential, b. impedance means coupling said collector electrode to said output terminal of said demodulator, c. phase shifting means including a unidirectional current conducting device having first and second terminals, said first terminal being coupled to said one input terminal of said demodulator, said device poled to conduct only for certain polarity excursions of said reference signal at said one input terminal, d. a capacitor coupled between said second terminal of said unidirectional current conducting device and a point of reference potential, said capacitor charging to a D.C. level due to said conduction of said device in accordance with said certain polarity excursions of said reference signal, e. means coupling the junction between said capacitor and said unidirectional current conducting device to said base electrode of said transistor to render the same nonconductive in accordance with said D.C. level, f. switching means coupled to said means (e), for forward biasing both said unidirectional device and said transistor during a first selectable mode, to cause said phase shifting means to shift the phase of said signals at said input of said demodulator and said impedance means serving to lower said amplitude at said demodulator output via said conducting transistor.

Claim 9

Apparatus for shifting the phase of a reference signal applied to one input terminal of a demodulator while simultaneously reducing the amplitude at the output terminal of said demodulator, comprising, a. a transistor having a base, collector and emitter electrode, said emitter electrode being coupled to a point of reference potential, b. impedance means coupling said collector electrode to said output terminal of said demodulator, c. phase shifting means including a unidirectional current conducting device having first and second terminals, said first terminal being coupled to said one input terminal of said demodulator, said device poled to conduct only for certain polarity excursions of said reference signal at said one input terminal, d. a capacitor coupled between said second terminal of said unidirectional current conducting device and a point of reference potential, said capacitor charging to a D.C. level due to said conduction of said device in accordance with said certain polarity excursions of said reference signal, e. means coupling the junction between said capacitor and said unidirectional current conducting device to said base electrode of said transistor to render the same nonconductive in accordance with said D.C. level, f. switching means coupled to said means (e), for forward biasing both said unidirectional device and said transistor during a first selectable mode, to cause said phase shifting means to shift the phase of said signals at said input of said demodulator and said impedance means serving to lower said amplitude at said demodulator output via said conducting transistor.

Claim 10

The apparatus according to claim 7 wherein said unidirectional current conducting device is a semiconductor diode.

Claim 11

In a color television receiver, including a chrominance channel having at least one color demodulator for demodulating chrominance signals contained in a composite television signal and applied to a first input terminal thereof with respect to a color reference oscillator signal applied to a second input terminal of said demodulator to obtain at an output terminal of said demodulator, color information signals of a first phase and amplitude, in combination therewith, apparatus for selectively altering the characteristics of said demodulators to provide color information signals of a phase and amplitude different from said first, comprising, a. a transistor having a base, collector and an emitter electrode, said emitter electrode being coupled to a point of reference potential, b. impedance means coupling said collector electrode to said output terminal of said demodulator, c. phase shifting means having first and second terminals and having said first terminal coupled to the input of said demodulator, d. a unidirectional current conductive device, having first and second terminals and haVing said first terminal coupled to said second terminal of said phase shifting means, e. a capacitive reactance coupled between said second terminal of said unidirectional current conductive device and a point of reference potential, f. a high impedance device coupled between the base electrode of said transistor and said second terminal of said unidirectional current conductive device, and g. switching means coupled to the junction of said high impedance device and said unidirectional current conductive device for forward biasing both said device and said transistor in a first mode of operation and rendering the same nonconducting during a second mode, whereby when said unidirectional conductive device is forward biased said phase shifting means causes a predetermined phase shift for said reference oscillator signals applied to said second terminal of said demodulator and said forward biasing of said transistor causes said impedance means to simultaneously lower the level at said output terminal of said demodulator.

Claim 12

In a color television receiver, including a chrominance channel having at least one color demodulator for demodulating chrominance signals contained in a composite television signal and applied to a first input terminal thereof with respect to a color reference oscillator signal applied to a second input terminal of said demodulator to obtain at an output terminal of said demodulator, color information signals of a first phase and amplitude, in combination therewith, apparatus for selectively altering the characteristics of said demodulators to provide color information signals of a phase and amplitude different from said first, comprising, a. a transistor having a base, collector and an emitter electrode, said emitter electrode being coupled to a point of reference potential, b. impedance means coupling said collector electrode to said output terminal of said demodulator, c. phase shifting means having first and second terminals and having said first terminal coupled to the input of said demodulator, d. a unidirectional current conductive device, having first and second terminals and haVing said first terminal coupled to said second terminal of said phase shifting means, e. a capacitive reactance coupled between said second terminal of said unidirectional current conductive device and a point of reference potential, f. a high impedance device coupled between the base electrode of said transistor and said second terminal of said unidirectional current conductive device, and g. switching means coupled to the junction of said high impedance device and said unidirectional current conductive device for forward biasing both said device and said transistor in a first mode of operation and rendering the same nonconducting during a second mode, whereby when said unidirectional conductive device is forward biased said phase shifting means causes a predetermined phase shift for said reference oscillator signals applied to said second terminal of said demodulator and said forward biasing of said transistor causes said impedance means to simultaneously lower the level at said output terminal of said demodulator.