JPS58212279A - Receiver of character broadcast - Google Patents

Abstract

PURPOSE:To receive the character broadcast in the best condition, by performing tuning with a reference start signal of the character broadcast taken as a reference. CONSTITUTION:A composite video signal is inputted to a character data detecting circuit 7 via a waveform shaping circuit 5. The detected character data is converted into a parallel data in 8-bit at a shift register 10. This parallel data is inputted to a framing code detecting circuit 13, where the frame synchronism is taken and is also subject to an error bit check at the same time. A framing code detecting circuit 13 generates a signal which rises at the end of point of time of a framing code being a reference start signal to reproduce various codes. This signal triggers a monostable multivibrator. An LED lights with an output of the monostable multivibrator. The correct tuning to the character broadcast is done while viewing the LED.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a teletext receiver that receives and displays teletext sent with information such as characters and graphics superimposed during the vertical blanking period of a television signal, and particularly relates to a teletext receiver that receives and displays teletext transmitted with information such as characters and graphics superimposed during the vertical blanking period of a television signal. This invention relates to a receiver that simplifies tuning adjustment.

Conventional teletext receivers adjust channel tuning by visually checking the image on the regular TV screen, and then determining the best position for teletext reception when viewing the normal TV image. They considered it to be the best position and made adjustments. However, the best visual position differs depending on the adjuster, and the receivable range for TV images is quite wide, so even if the visual position is the best, it is not the best position for teletext reception. It is not necessarily the position of As in the past, adjusting the best tuning position for visually seen television images as the best position for teletext reception is unreliable and may cause receiver malfunctions, giving the user a sense of anxiety.

The present invention has been made in view of the above facts, and provides a teletext receiver that can accurately adjust teletext reception to the best tuning position using a simple adjustment method without making adjustments based on television images. Particularly, in the present invention, a reference start signal (framing code) of teletext broadcasting is detected, its output is displayed by some method, and the best tuning position is adjusted using this display as a reference.

The present invention is particularly suitable when an EL (electroluminescence) display device or a liquid crystal display device is used as the display device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention shown in the drawings will be described below. FIG. 1 shows a block diagram of one embodiment of the present invention, in which an EL panel is used as a display device.

In FIG. 1, 1 is an antenna and 2 is a tuner. A television signal on which a character signal is superimposed is received by the antenna 1 and sent to the tuner 2. The tuner 2 performs high frequency amplification and frequency conversion as is well known, and inputs the signal to a video detection circuit 3 including a video intermediate frequency amplifier. tuner 2
The resulting video intermediate frequency signal is amplified and detected by a video detection circuit 3 to become a composite video signal, which is then input to a synchronization separation circuit 4 and a waveform shaping circuit 5. Synchronous separation circuit 4
Then, a vertical synchronizing signal S1 and a horizontal synchronizing signal S2 are extracted from the input composite video signal and output in order to synchronize each circuit and synchronize the EL panel display. 5 is a waveform shaping circuit, and the composite video signal inputted to this waveform shaping circuit 5 is sliced at an appropriate level after being subjected to appropriate amplitude and phase compensation, and is then sliced into transistors, transistors, etc.
The waveform is shaped to a logic (hereinafter referred to as TTL) level. T containing the character signal output from the waveform shaping circuit 5
The TL level signal is input to a character data detection circuit 7 controlled by a multiple gate generation circuit 6. The multiplex gate generating circuit 6 outputs a pulse (hereinafter referred to as multiple H) of one horizontal scanning width (hereinafter referred to as IH width) during the horizontal scanning period of a composite video signal on which character signals are multiplexed. The multiplex gate generating circuit 6 is configured with a counter and is reset by the vertical synchronizing signal S1 inputted from the synchronizing separation circuit 4, and when it counts the horizontal synchronizing signal S2 and finds that it matches the preset H, it falsely generates multiplexed H. Output. The above V'' multiple pulses are input to the character number detection circuit 7.

The character data detection circuit 7 gates the input TTL level signal from the waveform shaping circuit 5 using the multiple pulses, and detects a character signal (hereinafter referred to as character data) from the TTL level signal.

8 is a clock run-in signal (hereinafter referred to as CR signal), which is a synchronization signal for reproducing the pit clock, and C
This is a CR signal detection circuit that outputs a signal with an R signal width (hereinafter referred to as a CR sampling signal).

The CR pulse and CR sampling signal are created by the signal output from the waveform shaping circuit 5 and the multiple H output from the multiple gate generation circuit 6. The above CR number, CR sampling signal and multiple H are used in the write clock generation circuit 9 to convert the character data from serial to parallel into a shift register IO.
Creates a clock pulse to write to. The write clock generation circuit 9 is provided with a circuit for adjusting the phase of the character data clock. The character data is written to the shift register 10 by the write clock output from the write clock generation circuit 9, and
Converted to bit parallel data. The 8-pit parallel data is input to an Fc detection circuit (framing code detection circuit) 13 for frame synchronization, and is also subjected to an error pit check at the same time. The FC detection circuit 13 outputs a signal (hereinafter referred to as a PASS signal) that rises at the end of the framing code, which is a reference start signal constituting various codes, and falls at the end of the multiplexed H signal. The present invention uses this P ASS signal to
This detects the tuning of a television channel, and the details will be described later.

The PASS signal is input to the clock control circuit 12 together with the write clock output from the write clock generation circuit 9. The clock control circuit 12 uses the write clock as PAS.
A clock for writing effective character data is generated in units of a series of teletext broadcasts transmitted during one horizontal scanning period by gated by the S signal. The valid character data writing pulse is applied to the clock control circuit 12 along with the display clock output from the display clock generation circuit 11 which generates a display clock used when reading data from the pattern memory 14 etc. to be described later.
After inputting the signal to an OR gate (not shown), the frequency is divided.

The reason why the clock is frequency-divided as described above is because data is processed in units of 8 bits, that is, 1 byte. The display clock generation circuit 12 is phase-synchronized with the horizontal synchronization signal.Next, the character data converted into parallel data by the shift register 10 is stored in a buffer memory (included in the pattern memory 14) in byte units. ). Once writing of data to the buffer memory is completed, subsequent data processing is performed by a CPU (central control unit) 21. The character data written to the buffer memory is C
It is read out to PU21. The read character data is C
Only when the character data is decoded by the PU 21 and matches the program number designated in advance by the key input device 23, the character data is stored and held in the pattern memory 14 and color memory 15, respectively. Is the data stored in the pattern memory 14 as described above? The signal is read out by the lock into the P-S shift register 24 and subjected to parallel-to-serial conversion. The serially converted character data is sent to the EL drive signal mixing circuit 2.
5. On the other hand, the color data stored in the color memory 15 is not sent as color information to be displayed on a normal CRT display device, but is inputted to a color code conversion circuit 20 in order to extract only data for concealment or haflashing. . The color data inputted to the color code conversion circuit 20 is converted into a flashing or concealing control signal and inputted to the EL driving signal mixing circuit 25. E
In the L drive signal mixing circuit 25, the P-S shift register 2
The pattern data sent from the color code conversion circuit 20 is outputted to the EL panel 26, and the display of the pattern data displayed on the EL panel 26 is controlled by the flashing or concealment control signal sent from the color code conversion circuit 20.

The above is an explanation of the configuration and operation of a teletext receiver using the EL panel 26 as a display device.
Detection - By using the PASS signal output from '
This is intended to detect the tuning of a television channel by displaying that a PASS signal has been output from the C detection circuit 13.

FIG. 2 shows an example of a circuit that further embodies the reception status display device 27 for realizing the present invention, and by providing a display means as shown in FIG. That purpose can be achieved.

To explain this figure 2, as can be seen from the timing chart shown in figure 3, the pASS signal has only about an IH period (one horizontal scanning period), that is, 60 μs, so the pASS signal
The S signal is directly input to the transistor 29, and the LED 80
Even if you turn on the light, you can hardly confirm that it is on. So L
It is necessary to extend the "ON" period of the signal input to the base of the transistor 29 so that the lighting of the ED can be confirmed. In this embodiment shown in FIG. 2, a monostable multivibrator 28 is used to extend the ON period of this signal.
The rise of the ASS signal can be saved and the length of about IV period (one vertical scanning period), that is, 16m5K can be extended (see FIG. 4, ■).

In this way, by extending the "ON" period of the signal input to the base of the transistor 29, the lighting of the LED 30 can be confirmed.

When tuning a TV channel according to this embodiment, when receiving teletext at the best tuning position, IV (
This is because the pAss signal is detected at one or more locations (depending on the number of character signals superimposed on the TV image) in one vertical scanning period). The LED 30 blinks every second, so it appears to be completely lit, but if the TV channel is not tuned to the best position for teletext reception, the PASS signal may not be detected. becomes longer and the LED 30 appears to blink. Like this LE
By checking the lighting state of D and adjusting the TV channel tuning so that the LED is completely lit, the TV channel tuning can be adjusted to the best position for teletext reception. In addition, the tuning range for normal TV images is wider than the best reception tuning range for teletext reception, so even if you adjust the tuning of TV channels based on the teletext signal, the reception of normal TV images will not be poor. It is possible to adjust the reception status of both video and teletext according to the amount of grain.

As is clear from the detailed description above, the present invention provides a conventional general teletext receiver with a simple display circuit means as shown in FIG. , can be easily adjusted to the best channel tuning condition. Furthermore, even if the best tuning position for both normal television reception and teletext reception is far apart due to the frequency characteristics of the tuner, according to the present invention, it is possible to adjust to the best tuning position for teletext reception. can.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the teletext receiver of the present invention, Fig. 2 is an example of a circuit of a reception status display device used in the embodiment, and Figs. β and 4 are the same. It is a timing chart for explaining the operation of the embodiment. I3...E (i7. Detection circuit, 27... Reception status display device, 30... LEDo Agent Patent attorney Aihiko Fukushi (and 2 others),')・1

Claims (1)

[Claims] 1. In a teletext receiver that receives and displays text signals sent with information such as text and graphics superimposed during the vertical blanking period of a television signal, a reference start signal that is transmitted prior to the text signal data The present invention comprises a means for detecting a signal, and a means for displaying when the detected signal reaches an optimal reception state for teletext broadcasting, and tuning to a television channel can be performed based on the display. A teletext receiver featuring: