JPS6023550B2 - television receiver - Google Patents

Description

Detailed Description of the Invention In television broadcasting, within one horizontal scanning period within the vertical period of the video signal, a signal that does not need to have a relationship with the video signal, for example, sometimes Transmits information signals such as characters or symbols such as the latest news, weather forecasts, or other information, and erases parts of the image from the television image by operating it on the receiving side (receiver) A multiplexed signal transmission system has already been proposed in which the information signal is reproduced in the erased portion and viewed.

In this method, information signals to be transmitted are sequentially inserted into any one horizontal scanning period within each vertical line period of a television signal, and several fields, one term number field, several io fields, or the like are used. Desired information is transmitted within the above field period.
In this case, as the horizontal scanning period, it is generally said that 2G digits can be used starting from the front green of the vertical synchronization signal, and in the following explanation, this 2G digits (2G digits) in the sequential vertical retrace period can be used.
(However, this is not limited to this.) It is assumed that the signals are inserted into each horizontal scanning period. Also, as shown in Figure 1, information signals (hereinafter simply referred to as characters) are M in terms of length.
It is divided horizontally into N parts, so it is displayed with MXN dots, and in the example in Figure 1, M
=N=10, but in practice M=N=16 would be appropriate.

Note that an interval of two dots is required between each character. In this character transmission, each column M,,M2,M3,...
. is sequentially scanned to obtain a bit signal S corresponding to each dot, and therefore, in this example, a column of characters is represented by a 10-bit signal.

In this way, these signals are transmitted in the above-mentioned horizontal scanning period (hereinafter referred to as the H period) within each vertical blanking period, but first, they are transmitted during the H period (the H period) of the first vertical retrace period. In the H period of the second vertical retrace period (hereinafter referred to as the 3rd, 4th, etc. H period in order), the signal based on the column M, In the same way, the signals based on
A signal based on this is transmitted. Figure 2 is Cape No. 4 (vertical blade skin 4)
This shows the transmission status of .

In addition, when inserting the above-mentioned bit signal S into the H period in this way, since color television broadcasting actually uses a 3-band MHZ subcarrier signal, it is necessary to is stepped down to, for example, 1'2, and the above-mentioned bit signals are arranged in bottles at the signal interval using the signal thus obtained.

Note that a synchronization signal for determining the start position is inserted at the beginning of the signals arranged as described above. Further, a signal whose frequency is lowered to 1'2 of this subcarrier signal is designated as a pulse Po, its frequency is designated as fo, and its period is designated as To. With the above configuration, in this example, the first character (
In this example, h) can be transmitted.

However, in this example, an interval of 2 bits is maintained between the first character and the second character, so 12 fields are required in this example to transmit one character. I will do it. Regarding the second letter, the second letter is from the first theft item.
It is clear that each signal is transmitted in the H period (the second period is longer than the first sub-period) of the second direct retrace period. On the other hand, in the receiving device, as shown in FIG.
A memory circuit 1 having a memory circuit 1 is provided, and the encoded signal, that is, the bit signal transmitted as described above, is sequentially distributed bit by bit by an electronic switch 2 that switches one step for each bit. The data is stored in parallel to each other in the memories la to li, and readout pulses having a predetermined frequency are used to read data in each vertical period, that is, during a specific number of days (a day is one horizontal period) in each field. , is switched by an electronic switch 3 that is switched one step at a time for each horizontal scan, is supplied to a drive circuit 4, and is applied to a brightness electrode of a cathode ray tube 5. That is, the bit signal of the memory a is always asserted, for example, only on the 101st day of each field, that of the memory lb is always asserted only on the 102nd day of each field, and so on, and so on, and so on only in the corresponding horizontal period. Also, at the same time as the readout, the read bit signals are again sent to each of the memories 1a to li.
is memorized and cycled by the output pulse. Therefore, by appropriately selecting this presentation speed, this information can be reproduced on the cathode ray tube 5. In addition, in the above-mentioned case, the local subcarrier signal generated by the burst signal is used to generate the starting pulse, or the starting clock signal (
The repetition frequency is, for example, 2fo), and on the other hand, in order to display the above information at a predetermined position (with respect to the horizontal direction) on the cathode ray tube, the horizontal synchronizing signal, that is, the daily pulse PH is used as a reference, and from this The above-mentioned output pulses are counted and this information is displayed after a predetermined number of pulses have passed.

However, if the reception condition deteriorates, for example in a weak electric field, the burst signal will be disturbed by noise, and the frequency of the local subcarrier signal will fluctuate at the time the burst signal arrives.

In this case, the point in time when a predetermined number has been counted from the H pulse PH, that is, the position in the horizontal direction, will move in accordance with this frequency fluctuation, and the reproduced information will shift left and right, making it unsightly. The present invention avoids these drawbacks, and by determining a reference signal after the burst signal and counting readout pulses from this, a predetermined position can be determined regardless of frequency fluctuations of the burst signal. It was designed so that the information could be reproduced.

The television receiver according to the present invention will be explained below with reference to FIG. 6 is a color television signal input terminal, 7 is a band pass filter, and 8 is a color burst signal extraction circuit, for example, 3.5 mother MHZ obtained on the output side.
The burst signal is supplied to the oscillation circuit 9, and a local subcarrier signal of 3.5 MHZ is obtained at its output side.

As is well known, this signal is supplied to a color demodulation system for color television signals, and is also supplied to a circuit 1 for forming an output pulse.
01 is supplied. As this circuit 10, for example, a multiplier circuit that doubles the frequency is used. The output pulse (referred to as P) thus obtained is supplied to the counter 12 through the gate circuit 11 and also to the AND circuit 13.
On the other hand, the horizontal blanking pulse supplied to the input terminal 14 is supplied to the AND circuit 16 through the waveform shaping circuit 15. Further, the V pulse Pv and the H pulse Px are supplied to the vertical direction display gate circuit 201 through terminals 17 and 18, respectively, and the vertical period to be displayed, for example 1, is supplied to the output side of the vertical direction display gate circuit 201.
For example, one signal is obtained during the period from day 01 to day 110. This signal is supplied to the AND circuit 16, and its output is the first bistable circuit (hereinafter the bistable circuit is referred to as FF).
21. The output of the IFF 21 is supplied to the gate circuit 11 as a gate signal, and its leading edge is used as a trigger signal, which is sent to the IFF 22 as a set signal. The trailing edge of the output signal of the F22 is used as a trigger signal and supplied to the *F23 as a set signal, and the output signal is supplied to the AND circuit 13 described above. Note that the counter 12 outputs pulses PR and P when the count number is X and x2, respectively.
R2 are obtained and these are respectively used as the second reset pulse.
and fed to the second baits F22 and F23. According to the configuration described above, when the current horizontal scanning period is in the information display period described above, an output of 1 is obtained from the gate circuit 20, and at this time, the horizontal planking shown in FIG. 5C is performed. Since the signal S is supplied to the waveform shaping circuit 15, a rectangular wave signal S2 shown in FIG. 5D is obtained at its output side. Since this signal S2 is supplied to the IFF 21 through the AND circuit 16, it is set by the trailing edge of the signal S2, that is, the rising edge of the signal S2, and a rectangular wave signal S3 shown in FIG. is obtained. The leading edge of the signal S3, that is, the rising edge of the signal S3, sets the F22.
A rectangular wave signal S4 shown in FIG. 5 is obtained on the output side. Furthermore, due to the rise of the signal S3 mentioned above, the gate circuit 11
opens, the counter 12 starts counting the read pulses P shown in FIG. 5B, and counts X, at which point the pulse PR shown in FIG. Ru.

The trailing edge of the signal S4, that is, the falling edge of the signal S4 sets the second F23, and the signal S5 shown in Figure 5 is obtained at its output side. When the counter 12 counts X2, a pulse PR2 shown in FIG. 5G is obtained, and the pulse PR2 is F.
23 is reset. As a result, the IFF 21 is also reset and returns to its original state. Therefore, the gate circuit 13
It is open only during the period of the signal S5 shown in the figure, and the starting pulse P is sent to the output terminal 19 during this period. This output is connected to the read pulse input terminal 24a of the memory 1a shown in FIG.
is supplied to The same applies to the memories lb, lc, . . . . As is clear from the above explanation, the end point of the planking signal S shown in FIG. 5C, that is, the rising point (trailing edge) of the signal S2 shown in FIG. Normally, the timing is slightly delayed from the burst signal Sb in the burst signal Sb, and the information is reproduced from the falling edge of the signal S4, that is, when the pulse P is counted by X with this point as a reference. Therefore, even if a frequency shift of the burst signal Sb occurs during horizontal planking, it is irrelevant to the number of pulses P counted in the signal S4, and in the end, the trailing edge of the signal S4 with respect to the horizontal synchronization signal PH is always constant in the burst signal S4 regardless of the frequency shift.

Therefore, information is always reproduced at a constant position (with respect to the horizontal direction) on the screen. Note that during each horizontal scanning period in which no display is performed, the output of the gate circuit 20 is 0, so the above-mentioned operation is not performed.

As described above, the present invention has the feature that it is possible to always reproduce stable information signals regardless of the reception state.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an example of an information signal for explaining the present invention, FIG. 2 is a waveform diagram showing a part of the coded signal, FIG. 3 is a block diagram explaining a storage circuit, and FIG. 4 5 is a block diagram showing essential parts of a television receiver according to the present invention, and FIG. 5 is a waveform diagram for explaining the same. 8 is a band pass filter, 10 is a read pulse generation circuit, 11 is a gate circuit, 12 is a counter, 14 is a horizontal blanking signal input terminal, 15 is a waveform shaping circuit, 20 is a vertical direction display gate circuit, 21, 22, 23 are the first,
The second and third bistable circuits, 19 are output terminals. Figure 2 Figure 1 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1 Generate a clock pulse of a constant frequency based on a burst signal in an input video signal, and use the clock pulse to sequentially read out information signals stored in a storage circuit and display them on the screen of a cathode ray tube. The television receiver is provided with a counter that counts the clock pulses, and when the counter counts a predetermined number of clock pulses from the end of the horizontal blanking signal following the burst signal in the video signal, the display timing is determined. By obtaining a timing pulse indicating , and using the timing pulse to control the start of reading out the information signal from the storage circuit, the horizontal display position of the information signal on the screen of the cathode ray tube is made constant. A television receiver characterized by: