Superimposing system

Claim 2

A superimposing system comprising: a first oscillation circuit for generating a free-running oscillation output when burst signal of video signal is not fed, and generating an oscillation output, when burst signal of video signal is fed, phase-locked to the burst signal, a second oscillation circuit for generating an output where frequency divided signal of the output is phase-locked to the horizontal synchronizing signal of video signal, a modulator for modulating an added signal, using the output of the first oscillation circuit as a color subcarrier, reference clock selecting means for selecting the output of the second oscillation circuit as reference clock when superimposing, and selecting the output of the first oscillation circuit as reference clock when not superimposing, a foundation signal generating circuit for generating burst signal, horizontal synchronizing signal and vertical synchronizing signal on the basis of the free-running oscillation output of the first oscillation circuit when displaying only the added signal, a display timing circuit for controlling the display position of the added signal on the basis of the reference clock, and means for changing over the modulated added signal and video signal.

Claim 3

A superimposing system in accordance with claim 1, wherein: a generating circuit of added color difference signal for generating at least first and second added color difference signals by feeding an added signal is further comprised, and said modulator modulates the first and the second added color difference signals.

Claim 4

A superimposing system in accordance with claim 1, wherein: said video signal is of NTSC system.

Claim 5

A superimposing system in accordance with claim 1, wherein: said video signal is of PAL system.

Claim 6

A superimposing system in accordance with claim 4, wherein: a generating circuit of added color difference signal for generating at least first and second added color difference signals by feeding an added signal is further comprised, and said modulator modulates the first and the second added color difference signals.

Claim 7

A superimposing system in accordance with claim 5, which further comprises: a line detecting circuit for generating detection output by detecting normal or reverse phase of burst signal of the video signal by each line, and said modulator comprises a first modulation circuit for modulating the first added color difference signal on the basis of the output of the first oscillation circuit, and a second modulation circuit for modulating the second added color difference signal by the output of the first oscillation circuit which phase is inverted by every line on the basis of the output of said line detecting circuit.

Claim 8

A superimposing system in accordance with claim 6, wherein: said first oscillation circuit comprises: a voltage controlled oscillator and a phase detector in which a burst signal is fed to one of the inputs thereof, and the output of the voltage controlled oscillator is shifted in phase by 90° by every line on the basis of the detecting output of the line detecting circuit, and is fed to another input of the phase detector.

Claim 9

A superimposing system comprising: a first oscillation circuit for generating an oscillation output phase-locked to the burst signal of video signal, a modulator for modulating an added signal, using the output of the first oscillation circuit as color subcarrier, and means for changing over the modulated added signal and video signal.

Claim 10

A superimposing system comprising: a first oscillation circuit for generating an oscillation output phase-locked to the burst signal of video signal, a modulator for modulating an added signal, using the output of the first oscillation circuit as color subcarrier, and means for changing over the modulated added signal and video signal.

Claim 11

A superimposing system comprising: a matrix for obtaining a first color difference signal, a second color difference signal and a luminance signal by feeding an added signal, a burst gate for taking out the burst signal from video signal, a first PLL circuit having a phase detector which receives the output from said burst gate at one of its outputs, and receives an output from a voltage controlled oscillator at another input, a synchronous separating circuit for taking out a horizontal synchronizing signal from video signal, a second PLL circuit having a phase detector which receives the output from said synchronous separating circuit at one of its inputs, and receives a predetermined frequency divided signal of an output of a voltage controlled oscillator at another input, first and second added color difference signal modulators for modulating first and second added color difference signals, using the output of the voltage controlled oscillator of the first PLL circuit as color subcarrier, an adder for adding the modulated color difference signals and luminance signals to obtain a modulated added signal, a display timing circuit for controlling the display position of the added signal, using the output of the voltage controlled oscillator of the second PLL circuit as reference clock, and means for changing over the modulated added signal and video signal, on the basis of a changeover signal.

Claim 12

A superimposing system comprising: a matrix for obtaining a first color difference signal, a second color difference signal and a luminance signal by feeding an added signal, a burst gate for taking out the burst signal from video signal, a first PLL circuit having a phase detector which receives the output from said burst gate at one of its outputs, and receives an output from a voltage controlled oscillator at another input, a synchronous separating circuit for taking out a horizontal synchronizing signal from video signal, a second PLL circuit having a phase detector which receives the output from said synchronous separating circuit at one of its inputs, and receives a predetermined frequency divided signal of an output of a voltage controlled oscillator at another input, first and second added color difference signal modulators for modulating first and second added color difference signals, using the output of the voltage controlled oscillator of the first PLL circuit as color subcarrier, an adder for adding the modulated color difference signals and luminance signals to obtain a modulated added signal, a display timing circuit for controlling the display position of the added signal, using the output of the voltage controlled oscillator of the second PLL circuit as reference clock, and means for changing over the modulated added signal and video signal, on the basis of a changeover signal.

Claim 13

A superimposing system in accordance with claim 9, wherein said video signal is of NTSC system.

Claim 14

A superimposing system in accordance with claim 9, wherein: said video signal is of PAL system.

Claim 15

A superimposing system in accordance with claim 11, which further comprises: a line detecting circuit for generating detection output by detecting normal or reverse phase of burst signal of video signal in every line, said first modulator modulates the first added color difference signal on the basis of the output of the first PLL circuit, and said second modulator inverse the phase of the output of the oscillation circuit in every line on the basis of the output from said line detecting circuit, and modulates the second added color difference signal.

Claim 16

A superimposing system in accordance with claim 12, wherein: said first oscillation circuit comprises a voltage controlled oscillator and a phase detector having a burst signal fed to one of inputs thereof, and the output of the voltage controlled oscillator is shifted in phase by 90° in every line on the basis of the detecting output of the line detecting circuit, and feeds to another input of the phase detector.