GB2117207A

GB2117207A - Multiple system colour television receiver

Info

Publication number: GB2117207A
Application number: GB08305651A
Authority: GB
Inventors: Norio Abe
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1982-03-03
Filing date: 1983-03-01
Publication date: 1983-10-05
Also published as: JPS6321397B2; JPS58151187A; GB2117207B; DE3306708C2; GB8305651D0; DE3306708A1

Abstract

A multiple system color television receiver comprises a PAL chroma signal processing circuit 2, SECAM chroma signal processing circuit 3, a system selecting switch 4 connected to receive selectively the outputs of these circuits. A color killer circuit of the first chroma signal processing circuit 2 provides an output A which is high when a PAL chroma signal is detected, a color killer circuit of the second chroma signal processing circuit 3 provides an output B which is high when a SECAM chroma signal is detected. The signals A and B are supplied to a reset terminal R and a set terminal S of a RS flip-flop 8, respectively. The output C controls the system selecting switch 4. <IMAGE>

Description

SPECIFICATION Multiple system color television receiver Background of the invention Field of the invention The present invention relates to a multiple system color television receiver. More specifically, the present invention relates to a system selecting apparatus of a multiple system color television receiver adapted to be capable of selectively receiving either one system of at least two kinds of systems of the color signal of color television.

Description of the prior art As well known, the color signal of color television may be classified into two kinds of systems of the PAL system and the SECAM system. Depending on the countries or regions, two kinds of the color signal of color television of the PAL system and the SECAM system are adopted and depending on the locations either one can be received. In selling color television receivers in such area (such as Europe), it is necessary to provide multiple system color television receivers capable of receiving both systems.

Fig. 1 is a block diagram of a conventionally known system selecting apparatus of a multiple system color television receiver. The Fig. 1 conventional apparatus is disclosed in Japanese Patent Laying Open Gazette No. 161488/1980, the application of which was filed by the same assignee as that of the present invention. The Fig.

1 conventional apparatus will be described in the following.

A television signal received by an aerial and a tuner is supplied to a video detecting and amplifying circuit and a chroma signal obtained from the,video detecting and amplifying circuit is applied to an input terminal 1 in Fig. 1.

In the case where the chroma signal supplied to the input terminal 1 is a normal PAL chroma signal, a PAL chroma signal processing circuit 2 provides a demodulated signal D and a detected output A of the high level having determined that the chroma signal is of a PAL chroma signal is obtained from a terminal 1 OA. At that time, an output B of the low level is obtained from a detected output terminal 1 OB of a SECAM chroma signal processing circuit 3.The output B of the low level is inverted by an inverter 7 and the output B' of the high level is obtained from a terminal lOB'. Therefore, even when a detection selecting switch 5 of a manual selection type has been turned to any side, the output C from the switch 5 becomes the high level irrespective of which side, the PAL selection side or the SECAM selection side, has been selected by the detection selecting switch 5. The system selecting switch 4 is responsive to the output C of the high level to be automatically turned to the side of the PAL processing circuit 2 and the PAL demodulated signal D is obtained from the output terminal 6.

The output terminal 6 is coupled to a video output circuit, not shown, and the output therefrom is supplied to a cathode ray tube for display.

Conversely, in the case where the chroma signal supplied to the input terminal 1 of a normal SECAM chroma signal, the signals A, B and B' obtained from the above described detected output terminals 1 OA, 1 OB and lOB' and the output signal C of the detection selecting switch 5 become of the reversed level. More specifically, the signal A becomes the low level and the signal B becomes the high level and accordingly the signal B' becomes the low level and the signal C also becomes the low level. Accordingly, the system selecting switch 4 is responsive to the low level signal C to be automatically turned to the side of the SECAM processing circuit 3. Then the SECAM demodulated signal E demodulated by the SECAM chroma signal processing circuit 3 is supplied from the output terminal 6 to the above described video output circuit.

As described in the foregoing, when a conventional selecting apparatus is employed, it was possible to select a chroma demodulated output in a full automatic manner, as far as a normal PAL chroma signal and a normal SECAM chroma signal are concerned.

However, in the case of a reproduction output from a poor quality from a video tape recorder, particularly on the occasion of special reproduction, or in the case of an output obtained from reception in an area where a signal electric wave is weak, it could happen that the chroma signal supplied to the chroma signal input terminal 1 (see Fig. 1) becomes an abnormal chroma signal, as to be described subsequently.

In such a case, both the detected output A and the detected and inverted output B' do not coincide with each other such as in the high level or the low level. More specifically, when an abnormal PAL chroma signal is supplied, the output A is normally the high level; however, the output B also becomes the high level, with the result that the output B' becomes the low level.

Similarly, in the case of an abnormal SECAM chroma signal, although the output B' is the low level, the output A turns to be the high level. As a result, a disadvantage was caused that in spite of the fact that a PAL chroma signal has been received, the output C of the detecting switch 5 becomes the low level in accordance with selection by the manual detection selecting switch 5 and the system selecting switch 4 is turned to the side of the SECAM.

Of course, in such a case of reception of an abnormal chroma signal, the detection selection switch 5 may be operated by a customer or by a user so that the system selecting switch 4 may be turned to a proper state, so that a proper picture may be obtained; however, this necessitates manual operation of the detection selecting switch 5 of a manual operation type on the occasion of abnormality of the chroma signal, leaving a problem that the apparatus cannot be selected in a full automatic manner.

Summary of the invention Accordingly, a principai object of the present invention is to provide a multiple system color television receiver capable of automatically selecting the system in a full automatic manner, while a chroma signal system selecting switch is prevented from erroneously turned when an abnormal signal is received.

Briefly described, the present invention comprises a multiple system color television receiver, including a system selecting switch for selecting the outputs of first and second chroma signal processing circuits, and a flip-flop for providing a selecting signal to the system selecting switch, wherein the output of a first chroma signal detecting means and the output of a second chroma signal detecting means are supplied to one and the other inputs of the flipflop, whereby an output is obtained from the flipflop as a function of these two input signals, whereby the system selecting switch is turned.

According to the present invention, the system selecting switch need not be manually turned even in the case where an abnormal signal is received in a multiple system color television receiver adapted for displaying a picture based on the two system signals, whereby full automatic selection of a proper receiving signal can be made. Furthermore, it is possible to eliminate complexity of operating a manual switch which must be done at each occurrence of an abnormal picture.

These objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

Brief description of the drawings Fig. 1 is a block diagram showing a conventional system selecting apparatus of a multiple system color television receiver; Fig. 2 is a block diagram of a system selecting apparatus of a multiple system color television receiver in accordance with a preferred embodiment of the present invention; Fig. 3 is a block diagram showing in detail one embodiment of a PAL chroma signal processing circuit shown in Fig. 2; Fig. 4 is a block diagram showing in detail one embodiment of a SECAM chroma signal processing circuit shown in Fig. 2; Fig. 5 is a table showing the detection states of the kinds of the chroma signals in Figs. 1 and 2; Fig. 6 is a truth table of an RS flip-flop; Fig. 7 is a graph showing a time chart of the output states of the RS flip-flop responsive to the detected output of the Fig. 5 diagram;; Fig. 8 is a schematic diagram showing one example of the Fig. 2 system selecting switch; and Fig. 9 is a schematic diagram of another example of the Fig. 2 system selecting switch.

Description of the preferred embodiments Fig. 2 is a block diagram of a system selecting apparatus of a multiple system color television receiver in accordance with one embodiment of the present invention. A major difference of the Fig. 2 embodiment from the Fig. 1 conventional apparatus is that an RS flip-flop 8 is employed in place of the manual selecting switch 5. The RS flip-flop 8 comprises two NAND gates 8a and 8b coupled in a crossing manner. The detected output A of the PAL processing circuit 2 is supplied to a reset input terminal (R) of the RS flip-flop. The detected output B of the SECAM processing circuit 3 is supplied to the RS flip-flop 8. The output Q (i.e. the signal C) of the RS flipflop 8 is supplied to the system selecting switch 4 as a selecting signal.As to be described subsequently, the system selecting switch 4 serves to select the SECAM processing circuit 3 when the signal C is the low level and to select the PAL processing circuit 2 when the signal C is the high level, for example.

Fig. 3 is a block diagram showing in more detail the Fig. 2 PAL chroma signal processing circuit 2. The detected output A obtained from the detected output terminal 1 OA (Fig. 2) of the processing circuit 2 will be better understood when Fig. 3 is referred to.

The chroma signal supplied to the input terminal 1A is band pass amplified by a first and a second band pass amplifiers 201 and 202. The direct output and the output with a delay of 1 H by means of 1-H delay circuit 203 are subjected to addition and subtraction, respectively, whereupon the addition and the subtraction outputs are supplied to a B-Y demodulating circuit 204 and an R-Y demodulating circuit 205. On the other hand, a burst signal obtained from the burst gate circuit 206 is reproduced by an automatic phase control loop comprising an automatic phase control circuit 207 and a reference subcarrier oscillator 208 to provide a subcarrier wave. The subcarrier output is directly applied to the B-Y demodulating circuit 204 and is also applied through a PAL switch 209 to the R-Y demodulating circuit 205. The PAL switch 209 is responsive to the line output of the flip-flop to reverse the phase to +900 for each line. The outputs from the demodulating circuits 204 and 205 are obtained from the output terminals 9A1 and 9A2 as the output signals D1 and D2, respectively.

The output of the automatic phase control 207 is also applied to an identification and color killer circuit 211. The identification and color killer circuit 211 is responsive to the output from the automatic phase control 207 and the output from the flip-flop 210 to produce a color killer output and an identifying output. The color killer output is a direct current voltage output and is obtained as a disabling signal of the above described second band pass amplifying circuit 202 and is also obtained as a detected output from the terminal 10A.

Fig. 4 is a block diagram showing in more detail the Fig. 2 SECAM chroma signal processing circuit 3. Again the detected output B obtained from the detected output terminal 1 OB (Fig. 2) of the SECAM chroma signal processing circuit 3 would be better understood with reference to Fig.

4.

Referring to the Fig. 4 SECAM chroma signal processing circuit 3, the chroma signal supplied to the input terminal 1 B is supplied through a bell filter 301, a limiter 302, a 1-H delay circuit 303 and a line switch 304 to the B-Y demodulating circuit 305 and the R-Y demodulating circuit 306.

The signals supplied to the demodulating circuits 305 and 306 are in succession delayed by a 1-H period by means of the 1-H delay circuit 303 and the line switch 304. The burst signal obtained from the burst gate circuit 307 is detected by an FM detecting circuit 308 and the output is supplied to the identification and the color killer circuit 309. The identifying output of the identification and color killer circuit 309 and the line phase output from the flip-flop 310 serve to switch the line switch 304, whereby the color killer output of the identification, and the color killer circuit 309 are supplied to the two demodulating circuits 305 and 306 for the purpose of preventing noise signal demodulation.The demodulated signals obtained from the B-Y demodulating circuit 305 and the R-Y demodulating circuit 306 undergo deemphasis by deemphasis circuits 311 and 312, respectively, whereupon the demodulated outputs El and E2 are provided. The color output from the identifying and color killer circuit 309 is obtained as the above described detected output B from the terminal lOB.

In the foregoing, the detected outputs A and B and the demodulating outputs D and E of the embodiment were specifically described.

Fig. 5,is a table showing the detected outputs of the two systems with respect to the received signals for explaining the operation of the Fig. 2 diagram. Referring to Fig. 5, by an abnormal PAL chroma signal and by an abnormal SECAM chroma signal are each meant a case in which one detected output is normal while the other detected output is erroneous and are not meant a case where both detected outputs are erroneous.

More specifically, by an abnormal PAL chroma signal is meant a signal with which the SECAM processing circuit 3 erroneously detects the signal as a SECAM chroma signal in spite of the fact that the signal is a PAL signal, thereby to provide the output of the high level as the detected output B.

By an abnormal SECAM chroma signal is meant a signal with which the PAL processing circuit 2 erroneously detects the signal as a PAL signal in spite of the fact that the signal is the SECAM, thereby to provide the output of the high level as the detected output A.

Fig. 6 is a truth table of the Fig. 2 RS flip-flop 8.

Fig. 7 is a graph showing the time chart for explaining the output states of the RS flip-flop 8 with respect to the Fig. 5 detected output.

Fig. 8 is a schematic diagram of one embodiment of the Fig. 2 system selecting switch 4.

Referring to Fig. 8, the Q output, i.e. the signal C of the RS flip-flop 8 (Fig. 3) is supplied to the terminal 81. If and when the signal C is the high level, the transistor 82 is turned on and conversely the transistor 83 is turned off. As the result, the diode 84 is turned on and the diode 85 is turned off. Accordingly, the transistor 86 is turned off and the transistor 87 is turned on.

Therefore, the demodulated signal D of the PAL processing circuit 2 (Fig. 3) supplied from the terminal 9A is obtained from the output terminal 6.

Similarly, if and when the signal C is the low level, the transistor 82 is turned off and conversely the transistor 83 is turned on. As the result, the diode 84 is turned off and the diode 85 is turned on. Accordingly, the transistor 86 is turned on and the transistor 87 is turned off.

Therefore, the demodulated signal E of the SECAM processing circuit 3 (Fig. 3) supplied from the terminal 9B is obtained from the output terminal 6.

Fig. 9 is a schematic diagram of another embodiment of the Fig. 2 system selecting switch 4.

Referring to Fig. 9, the output Q, i.e. the signal C of the RS flip-flop 8 (Fig. 3) is supplied to the terminal 91. If and when the signal C is the high level, the transistor 92 is turned on and the relay coil 94 gives rise to an attracting force.

Accordingly, the relay contact 95 is turned to the D side (9A), whereby the demodulated signal D is obtained from the output terminal.

Similarly, if and when the signal C is the low level, the transistor 92 is turned off and the relay coil 94 does not give rise to an attracting force.

Accordingly, the relay contact 95 is turned to the E side (9B), whereby the demodulated signal E is obtained from the output terminal.

Now mainly referring to Figs. 2, 5 and 7, a specific operation of the embodiment shown will be described.

(1) An operation in the case where a normal PAL chroma signal is received.

When a normal PAL chroma signal is received, both of the detected output A obtained from the PAL processing circuit 2 and the detected output B obtained from the SECAM processing circuit 3 are properly detected outputs. Accordingly, the detected output Q becomes the high level and the detected output B becomes the low level. Since the detected output A of the high level is applied to the reset input terminal of the RS flip-flop 8, the output Q (i.e. the signal C) of the RS flip-flop 8 becomes the high level. Therefore, as described above, the system selecting switch 4 selects the PAL processing circuit 2, thereby to provide the demodulated output D to the output terminal 6.

(2) An operation in the case where an abnormal PAL chroma signal is received.

When an abnormal PAL chroma signal is received, the detected output A is normally the high level but the detected output B becomes an erroneously detected state (i.e. the high level: shown by the asterisk mark in the figure).

Therefore, both the set input and the reset input of the RS flip-flop 8 become the high level and the RS flip-flop maintains the previous state (Fig. 6).

Accordingly, the output Q remains unchanged as the low level. Therefore, even in the case where an abnormal PAL chroma signal is received, the demodulated output D of the PAL chroma signal is obtained from the output terminal 6.

(3) An operation in a reception state of a BAN signal.

When a B/W signal (black and white television signal) representing a blanking period or a write period is being received, both of the detected outputs A and B are the low level. Therefore, the output Q and the output Q of the RS flip-flop both become the high level and therefore the demodulating output B of the PAL chroma signal is obtained from the output terminal 6 (Fig. 3).

However, since a color killer operation of the SECAM chroma processing circuit 3 (Fig. 5) is being operated in such case, originally the demodulated signal does not appear and this does not cause any problem.

(4) an operation in the case where a normal SECAM chroma signal is received.

When a normal SECAM chroma signal is being received, the detected output A becomes the low level and the detected output B becomes the high level. Therefore, the output Q of the RS flip-flop 8 becomes the low level and the output Q thereof becomes the high level. Accordingly, the system selecting switch 4 is turned to the SECAM processing circuit 3 and therefore the demodulated output E of the SECAM chroma signal is obtained from the output terminal 6.

(5) An operation in the case where an abnormal SECAM chroma signal is received.

When an abnormal SECAM chroma signal is being received, both of the detected outputs A and B becomes the high level. In such a case, it follows that the detected output A represents erroneous detection. Therefore, both of the set input terminal and the reset input terminal of the RS flip-flop are supplied with the high level.

However, the RS flip-flop 8 maintains the previous state as a function of the high level through both inputs (Fig. 6), whereby no change occurs in the output and the output 9 remains the low level. Accordingly, the system selecting switch 4 is not selected at all and maintains a selection state of the processing circuit 3.

Therefore, the demodulated output E of the SECAM chroma signal is obtained from the output terminal 6.

Meanwhile, although the Fig. 2 was described by taking an example of the structure of the RS flip-fiop 8 implemented by the two NAND gates 8a and 8b, the same may be implemented by combining any other kinds of logical circuits. For example, the RS flip-flop may be implemented by combining two NOR gates.

In the foregoing description, the detected outputs A and B were obtained from the color killer circuit of the respective chromal signal processing circuit; however, this should not be taken by way of limitation. More specifically, the present invention may be practiced such that a separate signal detecting circuit is provided to supply a detected output to the flip-flop.

Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.

Claims

1. A multiple system color television receiver adapted for displaying an image upon selection of either a first system television signal or a second system television signal, comprising: first chroma signal processing means (2) for demodulating and processing a first chroma signal of said first system television signal, second chroma signal processing means (3) for demodulating and processing a second chroma signal of said second system television signal, system selecting means (4) for selecting either said first demodulated chroma signal obtained from said first chroma signal processing means or said second demodulated chroma signal obtained from said second chroma signal processing means, first signal detecting means (2, 211) for detecting -said first chroma signal, second signal detecting means (3, 309) for detecting said second chroma signal, and a flip-flop (8) receiving as one input the output from said first signal detecting means and as the other input the output from said second signal detecting means and providing a first and second logical state output as a selecting signal to said system selecting means.

2. A multiple system color television receiver in accordance with claim 1, wherein said first signal detecting means comprises a first color killer circuit (211) included in said first chroma signal processing circuit (2), and said second signal detecting means comprises a second color killer circuit (309) included in said second chroma signal processing circuit (3), the output of said first signal detecting means (2) being obtained from said first color killer circuit (211) and the outputfrom said second signal detecting means (3) being obtained from said second color killer circuit (309).

3. A multiple color television receiver substantially as herein described with reference to the accompanying drawings.