U.S. Philips Corporation

Martin H Johanndeiter

Detlef W Oldach

Johannes G Raven

Jurgen Ruprecht

Otto L Warmuth

Martin Schmidt

A circuit arrangement for a television receiver including a video text decoder (30), producing signals from the video text data from which control signals for a picture display device can be derived. The circuit arrangement further including a television signal decoder (1), deriving from the television signal via a low-pass filter arrangement (15) the luminance signal which can be taken from the luminance signal output (18). The low-pass filter arrangement (15) has a first attenuation characteristic for suppressing the chrominance signal and a second attenuation characteristic for allowing all video text data to pass. The second attenuation characteristic of the low-pass filter arrangement (15) is used during the period of time in which the video text data occur. The input of the video text decoder (30) is coupled to the luminance signal output (18) of the television signal decoder (1).

Circuit arrangement for a television receiver comprising a video text

The invention relates to a circuit arrangement for increasing the resolution of color contours. A slope detector detects the slope of the luminance signal and, when a predetermined slope value is exceeded, produces a detection signal for energizing a counter. The counter controls an edge enhancement circuit for a color difference signal, in which, as soon as the counter is energizing, the value of the color difference signal is stored and is available as an output signal. After a predetermined number of equidistant clock pulses has been counted, the edge enhancement circuit (7, 16) supplies the actual color difference signal value. If before the end of the counting operation, a new detection signal is produced, then the edge enhancement circuit briefly receives and stores the actual color difference signal value, and the counter starts a new counting cycle.

Circuit arrangement for increasing the definition of color contours of a

A color television signal receiver includes a circuit arrangement for demodulating an NTSC-encoded chrominance signal available as a sequence of digital values. An oscillator circuit (33), which has an accumulator (16) and a waveform converter (31) produces two sine-shaped reference signals which are applied to a demodulator circuit (2). The accumulator (16) includes a register (18) and a (first) modulo-adder (17). A phase comparator circuit (12) controlling the phase of the reference signal receives at least one demodulated signal during the occurrence of the color synchronizing signal. The sawtooth-shaped accumulator output signal is added in a second adder (26, 38) during a first switching position of a change-over switch (23, 34) to an adjustable value and is thereafter applied to the waveform converter (31). In the second switching position of the change-over switch (23, 34), which only occurs during the occurrence of the color synchronizing signal, the accumulator output signal is applied unchanged to the waveform converter (31).

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Hamburg, Germany

Martin H Johanndeiter