DE2819730A1 - SECAM TELEVISION RECEIVER WITH A SETTING ARRANGEMENT FOR THE COLOR REFERENCE LEVEL - Google Patents

Description

PHF. 77-28-4-1978

"SECAM" television receiver with a setting arrangement for the color reference level.

The invention relates to a "SECAM"

Television receiver with a clamp circuit arrangement for the color reference level, the one with a bell circuit contains designated bandpass filter and a generator to periodically reference signals with the quiescent frequencies fo (B-Y) and fo (R-Y) at times corresponding to an invisible part of the image To introduce switching means into the chrominance signals, which Reference signals after demodulating a reference level deliver for a clamp.

In the SECAM process, the coloring

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blanking level in each of the two signal paths of the demodulated color difference signals BY and RY (which are often referred to as "black level ¹¹ ") the rest frequencies fo (BY) and fo (RY) of the subcarrier of the chrominance signals B ¹ B and D'R.

In the standardized signals transmitted by the transmitter, the rest frequencies fo (B-Y) and fo (R-Y) only for four microseconds alternately with each Transmit trailing edge of the horizontal sync pulses; by the delay of the bell switching and the Demodulators can do the by demodulating these resting frequencies during a time interval for a sufficient amount of time voltages obtained for a short period of time are not used as reference voltages for accurate clamping of the Color reference level can be used after demodulation.

FR-PS 1 565 237 describes the introduction of the signals with quiescent frequencies during the horizontal blanking intervals into the chrominance signal in order to obtain reference levels for use in clamping after demodulation. This introduction will take place either downstream of the switch from two separate oscillators or upstream of the switch and downstream of the bell filter from a single oscillator whose frequency is switched. The good effect of such a system is only very seldom guaranteed.

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The invention has for its object to provide a general solution to the problem of fixing the Specify the reference level of the colors in the television receivers.

The invention offers the further advantage that a setting of the chrominance signal demodulators generated reference level becomes superfluous.

According to the invention is a television receiver according to the SECAM method with a clamping circuit arrangement for the color reference level, which contains, among other things, a band-pass filter called a bell circuit and a generator to periodically and alternately generate reference signals with the quiescent frequencies fo (B-Y) and fo (R-Y) to be introduced into the chrominance signals by switching means at times corresponding to a non-visible part of the image which reference signals provide a reference level for a clamping after demodulation, thereby characterized in that the switching means between at least one output of the generator for the signals with the Resting frequencies fo (B-Y) and fo (R-Y) and at least one Selective filter in at least one chrominance path for at least one of the chrominance signals (B-Y) and (R-Y) and are arranged for at least one of the reference signals with one of the frequencies fo (B-Y) and fo (R-Y).

It was found that if, the reference signals introduced behind the bell circuit

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will be the values of the reference values after demodulation have been obtained vary depending on the harmonic ratio of the reference signals.

According to the invention, the forwarding of the chrominance signals and the reference signals takes care of the same selective filter that the reference level after demodulation for the harmonic ratio of the reference signals are insensitive, which means that Also an adjustment of this level is unnecessary it is possible to use demodulators in integrated circuit technology called "coincidence" or "quadrature" to use for the harmonic ratio are extremely sensitive.

When using coincidence or quadrature demodulators, a zero adjustment is made for this superfluous, eliminating any change in the period of chromatic equilibrium of the received image is excluded.

The introduction of the signals with a frequency fo (B-Y) and fo (R-Y) upstream of the selective Filters, which can be a bell circuit, in particular enable the use of an oscillator in integrated circuit technology without inductive elements, Its output voltage has a higher harmonic ratio without any disadvantage can show what happens when an oscillator has output signals in square or wave form

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Triangle shape generated; also result from it. Transmission characteristics that are identical for the chrominance and the reference signals, which means that during demodulation of the signals mentioned the highest accuracy "is possible.

The switching means between the quiescent frequency generator and the entrance of the bells are advantageous. circuit arranged and they redirect for a fraction of the periods referred to as vertical blanking Phase jumps between the chrominance signal and the reference signal in the form of colored flags in the left part of the Avoid image.

Preferably the resting frequencies

fo (B-Y) and fο (R — Υ) obtained from an oscillator whose Frequency is controlled by the horizontal deflection using a programmable divider circuit.

The introduction of the signals with rest frequency fo (B-Y) and fo (R-Y) in the chrominance signal during the vertical blanking makes it possible, after the demodulation. lation to store the color reference voltages that as a result, they are particularly stable and free from interference; these stored reference levels are then selected Timings are re-introduced into the demodulated color difference signals B-Y and R-Y, whereby the clamping circuit arrangement with high accuracy the relative balance of the three primary colors of the transmitted

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Image can generate through. Use of the introduced Reference level as clamp level.

In such a case, the rule results

the introduction of the reference signals and the sampling of the corresponding demodulated signals with the aid of a pilot signal such a self-synchronization arrangement, which means that the times of sampling the reference level alternate in the B-Y and R-Y segments always occur if the signals correspond to the demodulated resting frequencies fo (B-Y) and fo (R-Y) are available in the relevant route: this means that every possibility of occurrence is at the same time Clamping error excluded.

Exemplary embodiments of the invention are explained in more detail below with reference to the drawing. It demonstrate:

Fig. 1 shows a bi-circuit of the color unit of a SECAM color television receiver in a first embodiment according to the invention,

Fig. 2 the block circuit of the color unit a SECAM color television receiver according to a preferred one Embodiment of the invention,

Fig. 3 ^a · · · 3d the process of introducing the frequencies fo (BY) and fo (RY) with the help of electrical. Signals in a SECAM receiver according to the invention,

Fig. H is a block diagram of a preferred

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Supplied embodiment of a part of an inventive s en SECAM receiver.

FIG. ^5a and 5t> the scanning of the zero reference level of the (BY) and (RY) -Strecken with - means of electrical .Signale by the arrangement according to Fig h.

Figures 6 and 7, the (RY) -. And (BY) signals of a color bar pattern, and in connection with the Fig h the operation when re-inserting the NuIlreferenzpegel during the Horizontalaustastintervalleii.

8 shows the basic circuit diagram of a ventilation circuit for a reception? according to the invention,

9 shows the basic circuit diagram of a sampling and re-introduction circuit for the zero reference level one of the transmission paths for the color difference signals of a SECAM television receiver according to the Invention.

In Fig. 1, an input terminal 1 is for Chroma signals connected to one of the contacts of a first switching stage 2, which is connected to a control terminal 3 for a switching signal connected to the vertical deflection frequency is.

Another contact of switching stage 2

is connected to the common contact of a second electrical switching stage k , which is connected to a control terminal 5 for a switching signal with a suitable frequency

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for example the half frequency of the vertical deflection is connected.

The two other contacts of the switching stage h are connected to a generator which contains two oscillators 6 and 7 for the quiescent frequencies fο (BY) and fo (RY), two frequency dividers 8 and 9 and two frequency comparison circuits 10 and 11, one input is connected to a terminal 12 for the supply of a signal at the horizontal scanning frequency.

The outputs of the comparison circuits

10 and 11 are with frequency control inputs of the oscillators 6 or 7 connected.

The common contact of the switching stage 2 is connected to the input of the bandpass circuit 13 »the called bell circuit, the output of which divides into two, the first path being direct with a first limiter i4a and the second with one second limiter i4b via a delay line 1j5 are connected.

The outputs of the two limiters i4a and i4b are connected to a switching circuit 16, whose Outputs with demodulators 17a and 17b, respectively are connected, the aforementioned changeover switch being equipped with a control terminal 18 to which a changeover signal is fed at half the line frequency.

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The deraodulators 17a and 17t> are with

a clamping circuit arrangement 28 which contains an input 30 and two outputs for color difference signals BY and RY. A signal is sent to input 30
fed that the clamping controls. The clamping should take place in the time in which the reference level is stretched
appear.

Apart from the arrangements specific to the invention which will be explained later, the effect of the circuit according to FIG. 1 is as follows:
the chrominance signal to the input of the bell circuit 6
is divided into two parts, one directly and the other delayed by the duration of one horizontal table line {6k / us). After passing through the limiters i4a and i4b, the direct and the delayed signals from the changeover switch 16 are fed to the correct demodulator and then demodulated in order to obtain the color difference signals BY on the upper path and the color difference signals RY on the lower path; These signals from the demodulators 17a and 17b reach the clamping circuit 28 for clamping the color reference level in the key difference signals.

The arrangement according to FIG. 1 works as follows: the input of the bell circuit is connected to terminal 1

via switching level 2 for the duration of the vertical blanking intervals tied together; i.e. for the duration of the

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Square pulses in Fig. 3a; otherwise the input of the bell circuit is connected to a common contact of the switching stage h , the state of this switching stage is determined by a signal of half the field frequency. controlled (Fig. 3b), which enables the highlighting of the frequency fo (BY) from the generator 6 for the duration of a field and the frequency fo (RY) from the generator for the duration of the following field (Fig. 3 ^C )

The rest frequencies fo (BY) and fo (RY) for introduction during the vertical blanking pulses are 4250 and kk06.25 kHz, respectively; With regard to the line frequency, the corresponding division factors are h 250 OOO / 15 625 = 272 and k k06 250/15 625 = 282.

The output frequencies of the oscillators 6 and 7 are via the dividers 8 and 9 by the comparison circuits 10 and 11 are compared with signals with horizontal deflection frequency fed to terminal 12, which signals either from the horizontal synchronizing circuits or directly from the horizontal deflection generator. The tensions from the comparison levels 10 and 11 control the output frequencies of the oscillators 6 and 7 to the exact values for the frequencies fo (B-Y) and fo (R-Y).

The resting frequency en fo (jB-Y) and f ο (R-Y) are alternately fed into the chrominance signal during the Yertical blanking pulses (Fig. 3d).

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In the arrangement of FIG. 1, the

Signals with the resting frequencies fo (B-Y) and fo (R-Y) from the oscillators 6 and 7 supplied in a closed circuit with the horizontal deflection frequency being controlled.

Of course, others can too

Types of oscillators that are open-loop stabilized are used, such as quartz · * · stabilized oscillators.

In addition, as was already indicated above, the oscillators 6 and 7 can be used without any disadvantage Waves of any shape, square or triangular impulses, deliver, as they are, for example, from certain astable devices are supplied in integrated circuits, their operation particularly economical can be.

In FIG. 2, in which the reference numerals are the same as in FIG. 1, one of the contacts of the switching stage 2 is connected to the output of an oscillator 21 with a variable frequency, which is coupled to one of the inputs of the comparator 10 via a programmable divider 22 , the control input for a signal for controlling the division factor of this circuit is connected to the terminal h of the signals with the vertical half-frequency.

In the embodiment of the

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The result is only one oscillator * with variable frequency and one programmable Divider obtained, whereby the switching stage of FIG. 1 can be omitted.

The frequency of the controlled variable frequency oscillator 21 is set via the programmable Divider 22 compared with the line frequency to comparator 10 at terminal 12; the output voltage alternately changes the frequency of the oscillator 21 between the values fo (B-Y) and fo (R-Y), where the Ratio of divider 22 under the control of terminal 5 is alternately 272 or 282.

It should be noted that the introduction of the frequencies fο (B-Y) and fο (R-Y) just before the frequency change of the oscillator 21 takes place; in this way the introduced frequency is available for the full duration via a partial image for the corresponding stabilization.

In Fig. 4, in which the reference numerals are the same 1 and 2, contains the more detailed circuit diagram of the preferred embodiment of the invention Arrangement an amplifier 23 for the attenuation compensation of the delay line 15 as well a circuit 19 »the sampling and according to the invention Performs reintroduction function. The outputs of the Demodulators 17a and 17b come with two sampling circuits 24a and 24b coupled, which are operated by two new

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introductory circuits 25a and 25b are followed, where the connection between them is made by two storage capacitors 26a and 26b, which are connected to a common Ground contact 27 are connected.

The reintroduction circuits 25a and 25b each with an input in connection with a terminal 20 for the supply of line blanking pulses are with a circuit 28 for the mixing, amplification and clamping of the color difference signals Β-Ύ and R-Y, this circuit, which also has an input terminal 29 for brightness signals Y and an input terminal 3 ° for clamping signals contains the clamped blue, red and green color signals for controlling the electron gun supplies.

The control input of a bistable multivibrator 31 is connected to terminal 3 for the vertical blanking pulses. One of the complementary outputs of the multivibrator 31, the terminal 5 i ⁿ Fig. And 2 represents, is connected to the control input of progratnmierbaren divider 22, which is a part of the generator system of the frequency fo (BY) and fo (RY).

The complementary outputs of the multivibrator 31 are connected to the first inputs of the two AND gates 32a and 32b connected to two inputs, where the second inputs of these gates are connected to terminal 3 for the vertical blanking pulses. the

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Outputs of gates 32a and 3 ^21:> are connected to sampling circuits 24a and 24b, respectively.

The sampling and reintroduction circuit 19 operates as follows: starting from the vertical 'blanking pulses (Fig. 5a), the multivibrator "} Λ generates two complementary state signals (Fig. 5b and 5c) at its two outputs, which are sent to the two AND gates 32a and 32b, the other inputs of which receive vertical blanking pulses via terminal 3.

As a result, terminals 3 ^ a and 32b deliver

one impulse each, which occurs every second field ^; repeatedly (Fig. 5d and 5 ©)> which pulses to the circuits 24a and 24b sample the reference voltages VRB (Fig. 5f) and VRR (Fig. 5 &), which result from the demodulation of the frequencies fb (BY) and fo (ß -Y) after insertion through circuit 2.

The patterns of the voltages VRB and VRR

are stored in capacitors 26b and 26a, respectively, and at each horizontal return shoulder in the path B-Y (Fig. 7) and in the path R-Y (Fig. 6) are newly introduced by each of the circuits 25b and 25a, which are via the terminal 20 can be controlled by horizontal blanking pulses.

The reference levels VRB and VRR are precisely defined for each line and independent of the ratio the harmonics of the oscillator 21; a setting

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ment of this reference level becomes superfluous, whereby the Use of de-modulators in integrated circuits of the coincidence or quadrature type becomes possible.

The new introduction of the reference level takes place ■ during the horizontal blanking intervals, whereby it is possible to use the same signals that are fed to the input of the comparator 10; under these conditions, the terminals 20 and 12 can be combined, which is indicated by a dashed line in

.10 circuit diagram according to FIG. 4 is shown.

In Fig. 8, in which the reference numerals are the same as in Figs. 1, 2 and 4, the lead-in circuit 2 includes a positive conductor 33 and a negative 34 connected to two terminals 35 and "} 6 of a voltage source Vb, where the negative pole of this source is also connected to the common ground contact 27.

A resistor chain 37j 38 and 39 is arranged between the conductors 33 and ^ k , the common point of the first two being connected to the base of a transistor 40 of the npn type. The common point of resistors 38 and 39 is connected to the base of a transistor 42 of the npn type, the emitter of which is connected to the connection with the emitter of a third transistor 42, also of the npn type, via a resistor 43 to the capacitor 34 .

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The collector of transistor 4O is connected directly to the positive capacitor 33 while the emitter through two resistors 44 and 45 with the Collectors of transistors 41 and 42 is connected. The bases of transistors 41 and 42 are Via a capacitor 46 to terminal 3 for the vertical blanking pulses coupled, the first via a resistor bridge 47 and 48 and the second directly.

The interconnected emitters of the two groups of transistors 49-50 and 51-52 of the npn type are connected, the first with the. Terminal 1 for the chrominance signals and the second with the collector of a transistor 53 of npn type, the base of which with the The oscillator 21 and its emitter are connected to the conductor 34 via a resistor 54.

The bases of transistors 49 and 5 ² are connected to the collector of transistor 41, while the bases of transistors 50 and 5I are connected to the collector of transistor 42. The collectors of transistors 49 and 51 are connected directly to the positive conductor 33, while the collectors of transistors 50 and 52 are connected to the emitter of a transistor 55 of the npn type, the base of which is connected to a resistor bridge 56-57 between the conductors 33 and Jk is connected '.

The collector of transistor 55 is

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on the one hand via the bell circuit I3 with the conductor 33 and on the other hand with the inputs of the limiter i4a and the delay line I5.

The introductory circuit in Fig. 8 operates as follows: transistors 49 »30» 51 and 52. ' form a changeover switch controlled by transistors 41 and 4-2. If there are no Vertika3_austas timpulse at terminal 3, transistor kl conducts and transistor 42 is blocked; under these conditions, the transistors 50 and 5I conduct and the transistors 49 and 52 are blocked. As a result, the chrominance signals at terminal 1 are controlled via the transistors 50 and 55 on the direct and delayed paths, whereas the signals generated by the oscillator 21 are sent directly to the positive conductor 33 via the transistor 51

With a positive vertical blanking impu3.s the situation described is reversed at terminal 3, the transistors 42, 49 and 52 conduct and the Transistors 41, 50 and 5I are twisted; Under these Conditions are the chrominance signals that arrive at the conductor 33, while the reference signals fo (B-Y) and fo (R-Y) after every second field over the direct and delayed paths (Fig. 3d) can be controlled.

'The buffer transistor switched in cascode 55 lowers the output impedance of the collectors of the trans-

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sistors 50 and 52 and suppresses also possible crosstalk between the two signals dxirch the Stray capacitance emitter — collector of the blocked transistor.

In Fig. 9, in which the reference numerals are the same as those in Figs. 1, 2 and ^ t, the sampling and reintroduction circuit I9 contains two transistor pairs ^ 8-

59 and 60-61 of the npn type, the emitters of which are connected two and two to the collectors of two other transistors 62 and 63, also of the npn type, one of whose bases is connected to the output of the gate 32b and the other to the terminal 20 of the horizontal blanking signals are connected, the emitters of which are also connected to the negative conductor 2> h via two resistors 6h and 65.

The bases of the transistors 58 and 61 are connected through a resistor 66 and one of them is connected to the output of the demodulator 17b and the other to one of the inputs of the circuit 28 for mixing and amplifying the color difference signals.

The collectors of transistors 58, 59,

60 and 61 are connected to the collectors of two other transistor pairs 67 »68, 69 and 70, respectively, of npn type, whose bases are each two and two connected to the emitters of these four transistors, which are directly connected to the Conductor 33 are connected.

JThe collectors of transistors 59 and

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are connected to the bases of the transistors 59 and 6o via a resistor 71, while the collectors of the transistors 61 and 70 are connected to the base of the transistor 61 via a resistor 72. In addition, the bases of the transistors 59 and 6o are connected to the positive plate of the storage capacitor 26b.

The collectors of the two transistors 73 and 7h of the npn type are connected directly to the conductor 3 ^, the emitters being connected directly to the corresponding bases of the transistors 67-68 and 69-70; the collector of another transistor 75> also of the npn type, is connected to the bases of the transistors 69 and, while the emitter is connected directly to the conductor 33. ■ ·

- The bases of transistors 73 and 7 ^ are directly to the collectors of transistors 58-67 resp. 60-69 connected while the base of the Ti-ansistor 75 connected to terminal 20 via a resistor 76 is.

The sampling and reintroduction circuit 19 operates as follows: In the absence of horizontal or vertical blanking signals at the bases of transistors 62 and 63, these transistors and all others are blocked and the demodulated signals of the route used, e.g. on the blue route, are sent via resistor 66 to BY input of the circuit for mixing

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and gain 28 transmitted.

When the output gate 32b

(Flg. 5d) when a vertical blanking pulse of two is applied to the base of transistor 62, the latter becomes conductive, as a result of which transistors 58 and 59 are turned on; These two transistors form a differential amplifier to which a "current mirror" from the transistors 67 »68 and 73 is assigned, the resistor 71 ensuring complete negative feedback; Because of the very high gain of the unit, the reference voltage VRB (FIG. f) is sampled to the base of transistor 58 and is also applied to the base of transistor 59j, thereby bringing capacitor 26b to the VRB voltage value. When the vertical return pulse to transistor 62 disappears, the charge on capacitor 26b remains on the VRB for the entire duration of two fields; this VRB voltage is thus stored and reintroduced at each horizontal blanking interval with the aid of a second differential amplifier, the structure of which is the same as that of the first

is. '. ;

For the entire duration of the horizontal blanking intervals which unlock transistor 63, the VRB reference voltage, which is tapped off via transistor 60, is at the base of transistor 61 and starts at the input of circuit 28 (FIG. 6).

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Due to the high value of the capacitor 26b and the very weak "" at each horizontal blanking interval tapped from the base of transistor 60, the VRB voltage is almost constant between · Two consecutive charges of the aforementioned Capacitor.

It is the job of the transistor 75 »

to dissipate the stored charges on the bases of the transistors 69 and 70 which would otherwise tend to maintain the conductive state after the disappearance of the horizontal blanking pulses; For this purpose, the transistor 75 blocked by the "positive pulses from terminal 20" is switched on when these pulses disappear .

'A completely identical second circuit

compared to that in Fig. 9 is used for treatment of the R-Y path is used to feed the corresponding input of the mixing and amplifying circuit 28. In the preferred embodiment as described, the reference levels are reintroduced in the color difference signals B-Y and R-Y every horizontal blanking interval; theoretically, this operation will be carried out in a slow pace in terms of limitation during the vertical blanking interval hindered by nothing.

In this case, terminal 20 is sufficient

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with the help of the repetition frequency signals with suitable Supply duration to accomplish the desired task.

In the above-mentioned statements the reference signals upstream of the Glocicen filter in the SECAM chrominance signal was introduced. There the two are

Color difference signals alternately there, modulated on theirs appropriate carrier. It is of course also possible to introduce the reference signals to another Digit when the modulated color difference signal and the corresponding reference signal are passed through the same selective filter before they be demodulated. The circuit arrangements of the exemplary embodiments described have the advantage that no additional filters are required.

The clamping periods can be independent of

chosen the periods of introduction of the reference signals if a sampling and new introduction circuit is used. A reference signal does not then need to be converted into the corresponding modulated color difference signal are reintroduced when the modulated color difference signals and the reference signals through the same

Selective filters are performed,
ν

If no sampling and re-introduction circuit is applied, the introduction of the reference signals and the clamping of the corresponding demodulated Signals must of course happen in corresponding periods.

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Claims (1)

/ YJM. 28-4-1978. PATENT CLAIMS. t \ λ SECAM television receiver with a clamping circuit arrangement for the color reference level, the inter alia . a band pass filter called a bell circuit contains, and a generator to periodically reference signals with the rest frequencies fo (B-Y) and fo (R-Y) Points in time corresponding to a non-visible part of the image by switching means into the chrominance signals introduce what reference signals after demodulation provide a reference level for a clamping, characterized in that the switching means between at least one output of the generator for the signals with the quiescent frequencies fo (B-Y) and fo (R-Y) and at least a selective filter in at least one chrominance path for at least one of the chrominance signals (B-Y) and (R-Y) and for at least one of the reference signals with a the frequencies fo (B-Y) and fo (R-Y) are arranged. 2. Television receiver according to claim 1, characterized in that the switching means between the Generator for the resting frequencies fo (B-Y) and fo (R-Y) and the input of the band-pass filter designated by the bell circuit, wherein the bell circuit is used as a selective filter. 3. Television receiver according to one of claims 1 or 2, characterized in that those mentioned under 1 Switching means for a fraction of the vertical 8098A5 / 1022 PHF. 77,536 C. 28-4-1978. 281973Q blanking designated periods are conductive. H. Television receiver according to one of the claims 1, 2 or 3 »characterized in that one of the resting frequency generator generated waveform is substantially rectangular. 5 »TV receiver according to one of the claims 1, 2 or 3j characterized in that .that the Quiet frequency generator generated waveform is essentially triangular. 6. Television receiver according to one of the claims 1, 2 or 3j characterized in that the generator an oscillator for the rest frequencies fo (B-Y) and fo (R-Y) contains, the output of which is connected to an input of a frequency divider, whose Asugang with the Input of a frequency comparator is connected, of which another input terminal is connected to an output terminal a signal generator with the horizontal scanning frequency is connected, the output terminal of the frequency comparator to a frequency control input of the oscillator connected. 7 · Television receiver according to claim 6, characterized characterized in that the frequency divider is of the programmable type and includes a control terminal which is connected to a pulse generator which periodically calculates the partial factor of the circuit mentioned of the horizontal scanning frequency to the corresponding two values of the quotient of the resting frequencies fo (B-Y) and 809845/1022 PHF. 77 · 536.C 28-4-1978. 28-4-1978 fo (R-Y) adjusts. 8th. . Ferns eliempfanger according to one of the claims 1 to 7 »characterized in that the switching means are implemented in the form of an introductory circuit, which contains two transistor pairs in a switching arrangement, its first input with a terminal for vertical sampling frequency signals and its second input with a terminal for video frequency chrominance signals, and their third input to the output of the generator füx- the rest frequency en fo (B-Y) and fo (R-Y) connected and its output with the input terminal of the bell scarf is actively coupled. 9 «TV receiver according to claim 7 or 8, characterized in that the control pulse generator is a bistable! ¹ multivibrator whose trigger terminal is connected to the second input of the introductory circuit, with one of the two outputs of the complementary logic states of the multivibrator mentioned simultaneously to the control terminal of the programmable divider and to one of the inputs of a first AND gate and the other output to one of the inputs of a second AND gate are connected, the two other inputs of the said AND gates with the second input of the introduction circuit and the outputs with corresponding control inputs of a circuit for patterning and re-introducing the color reference level in the color difference signals B-Y and R-Y are connected. 809845/1022 PHF. 77-536.C, 28-4-1978. 10. Television receiver according to claim 9 »characterized in that the sampling and reintroduction circuit contains a reinfusion control terminal connected to a signal generator for the vertical scanning frequency is. 11. Television receiver according to claim 9 »characterized in that the sampling and reintroduction circuit contains a new lead-in terminal connected to a signal generator for the horizontal scanning frequency is. 12. Television receiver according to claim S, 10 or 11, characterized in that the sampling and reintroduction circuits both contain two transistor pairs which are arranged as differential amplifiers with an arrangement of the "current mirror" type between the two collectors of the transistors of one of the above Pairs is combined. 13 · Television receiver according to one of the claims 1 to 7 »dadurcli marked that the demodulated Color difference signals B-Y and R-T either for the duration of the visible image to a mixing and amplifying circuit for the color signals or for the duration of the Vertical blanking intervals get to a storage capacitor. 8Q9845 / 1022