JPS6315791B2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a magnetic recording device.

Conventionally, the nHth (17th and 18th H in CEEFAX)
Digital additional signal (representing characters, symbols, figures, etc.) superimposed on the 20th H in our country)
The television signal containing the information was recorded on a magnetic recording device as is.

However, in such a magnetic recording device, the transmission path of the television signal causes large waveform distortion, making it difficult to accurately reproduce the additional signal.

The first solution to this problem is
A magnetic recording device shown in FIGS. 4 to 4 has been proposed.

In FIG. 1, 1 is a video detection circuit of a normal television receiver, 2 is a data reproducing circuit, 3 is a switching circuit that switches and outputs the output of the video detection circuit 1 and the data reproducing circuit 2, and 4 is the magnetic recording device itself. (for color or black and white), and 5 is an additional signal receiving and reproducing device. In the following explanation, as an example of an additional signal
Considering CEEFAX, only the 17th H is considered as the superimposed section.

The output of the video detection circuit 1 is the code superimposed on the 17th H, as shown in FIGS. 3A and 3B (FIG. 3B is an enlarged view of the time axis of FIG. 3A). Both the amplitude and the phase of the waveform of the converted signal a are distorted compared to the waveform sent out by the television broadcasting station in FIG. 3C. Therefore, in the data reproducing circuit 2,
The waveform of FIG. 3B is sampled by the sampling clock of FIG. 3D to obtain the waveform of FIG. 3E. Then, the waveform shown in FIG. 3E is replaced by the waveform shown in FIG. 3B at the 17th H of the television signal by the switching circuit 3, and the terminals 6 and 7 are connected and recorded in the magnetic recording apparatus main body 4. The reproduction output of the magnetic recording device main body 4 is taken out from the terminal 8, and by connecting it to the terminal 9, the additional signal receiving and reproducing device 5 receives the reproduction output of the magnetic recording device and displays characters, symbols, or figures. The magnetic recording device main body 4 is commercially available, and the additional signal receiving and reproducing device 5 is also commercially available as a teletext adapter in the UK.

Next, the data reproducing circuit 2 and the switching circuit 3 will be explained in detail. In FIG. 2, the slice circuit 10 shapes the waveform of FIG. 3B into the waveform of FIG. Outputs the detection pulse b shown in FIG. 4B,
The 17H extraction circuit 13 extracts only the 17th H from the output of the slice circuit 10 using the detection pulse b of the 17H detection circuit 11. The switching pulse generation circuit 14 is composed of a monostable multivibrator that delays the start and a flip-flop, and the 17H detection circuit 1
1 (FIG. 4B) generates a switching pulse c as shown in FIG. 4C, and the trailing edge of the switching pulse c is determined by resetting the flip-flop with a horizontal synchronizing signal. On the other hand, the clock generation circuit 15
Clock run-in signal d shown enlarged in Figure D
outputs a sampling clock synchronized with the data on the transmitting side. There are two ways to create this sampling clock: a method in which a gated oscillator is gated at the leading and trailing edges of the clock run-in signal d, and a method in which a crystal resonator is used. Among these methods, methods using a crystal resonator include a ringing method and an injection clock method, and the sampling clock of the output of the clock regeneration circuit 15 is as shown in FIG. 3D. D flip-flop 1
6 is for data reproduction, and if the phase difference between the sampling clock and the output data is ignored, the waveform shown in FIG. 3E can be obtained as an output. Buffer amplifier 17 is D
The output of the flip-flop 16 is converted to a level balanced with the output of the video detection circuit 1. The analog AND gates 18 and 19 are MOS IC analog gates, etc., and the analog AND gates 18 and 19 and the inverter 20 normally supply the output of the video detection circuit 1 to the buffer amplifier 21 and output it from the terminal 6. , the output of the buffer amplifier 17 is supplied to the buffer amplifier 21 and output from the terminal 6 only during the period when the switching pulse c exists (high level period). As a result, the coded signal a shown in FIGS. 3A, B and 4A is replaced with the waveform of FIG. 3E. Therefore, the television signal is supplied to the magnetic recording device main body 4 after only the digital additional signal superimposed thereon is waveform-shaped. When the reproduction output of the magnetic recording device main body 4 is applied to the additional signal receiving and reproducing device 5, the additional signal is reproduced in the same way as when a broadcast television signal is received, and characters, symbols, or figures are displayed. In addition, in this proposed example, coded signal a was used as the additional signal, but instead of this, characters,
It may also be a decomposed pattern of symbols or figures. Further, in the above explanation, only the 17th H has been described, but the same processing may be performed for the 18th H. In this case, the pulse in Figure 4B is 2H
4, the pulse shown in FIG. 4C is generated every horizontal period, and the pulse shown in FIG. 4C is gated by the pulse shown in FIG.
It can be extracted as the output of 4.

In this way, the magnetic recording device of this proposed example extracts the additional signal superimposed on the television signal, shapes the waveform, and replaces it with the additional signal at the original position. The waveform distortion of the signal is eliminated, and the additional signal can be accurately reproduced because only the waveform distortion during recording occurs.

However, some magnetic recording devices cannot record video signals during the vertical retrace period and cannot record additional signals. In this case, the above proposed example cannot be used to record additional signals. I couldn't do it.

Therefore, an object of the present invention is to provide a magnetic recording device that is capable of recording additional signals sent during the vertical retrace period even with magnetic recording means that cannot record video signals during the vertical retrace period. It is to be.

An embodiment of this invention is shown in FIG. That is, in this magnetic recording device, in order to waveform-shape the additional signal superimposed on the 17th H, and then superimpose it on another horizontal period, for example, the 21st H, the 21H detection circuit 24 is added to the circuit shown in FIG. memory 25, NOR gate 26, gated oscillator 7, flip-flop 28 controlling gated oscillator 27 and x
A bit counter 29 is added. To explain in detail, first, in the 17th H, the x-bit coded signal a shown in FIG. 4A is transferred to the 1H memory 25.
is written. That is, the sliced data as shown in FIG. 6A is transferred to the D flip-flop 16.
When applied to the D terminal of the clock regeneration circuit 15,
Since the output of the D flip-flop 16 has the waveform shown in FIG. 6B, the Q output of the D flip-flop 16 becomes as shown in FIG. 6C. On the other hand, the output of the NOR gate 26 is shown in FIG.
The data shown in Figure 6E is now stored in the 1H memory 25.
It will be stored as the waveform shown in . Also, unlike the proposed example, the output of the switching circuit 14 becomes high level at the 21st H, and its rise (leading edge in Figure 4 C)
When the flip-flop 28 is set, the Q output of the flip-flop 28 becomes high level and the gated oscillator 27 oscillates. The oscillation frequency of this gated oscillator 27 is selected to be equal to the output frequency of the clock regeneration circuit 15. Therefore, the
At the 21st H, data is read from the 1H memory 25 by the clock of the gated oscillator 27. This data is replaced with the 21st H video signal via the buffer amplifier 17 in the same manner as in the above-mentioned proposed example. When the counter 29 counts the output pulses of the gated oscillator 27 by x bits, the flip-flop 28 is reset by the output, and the operation of the gated oscillator 27 is stopped.
Note that when recording the 18th H as well, the obtained data may be replaced with the 22nd H video signal. Further, when the additional signal recorded in this manner is to be reproduced by the additional signal receiving and reproducing device 5, the extraction gate of the additional signal receiving and reproducing device 5 may be shifted after four horizontal periods.

As a result of this configuration, it becomes possible to reproduce the additional signal even in a magnetic recording device of the type that erases the video signal during the vertical retrace period. As described above, the magnetic recording device of the present invention extracts the digital additional signal included in a specific horizontal period of the television signal by shaping the waveform using the shaping extraction means,
The switching means normally outputs the television signal, and the video signal of the horizontal period and the output of the shaping extraction means are switched and output in a horizontal period different from the horizontal period in which the digital additional signal is included, so that the video signal of the vertical blanking period is This has the advantage that even a magnetic recording means that cannot record data can record the digital additional signal sent during the vertical retrace period.

[Brief explanation of the drawing]

1 and 2 are a configuration diagram and a main block diagram of a proposed example of a magnetic recording device, respectively, FIGS. 3 and 4 are signal waveform diagrams for explaining its operation, and FIG. 5 is a diagram of the present invention. FIG. 6 is a block diagram of a main part of one embodiment, and a signal waveform diagram for explaining its operation. 1... Video detection circuit, 2... Data reproduction circuit,
3...Switching circuit, 4...Magnetic recording device main body, 5...
...Additional signal reception and regeneration device, 10...Slice circuit, 11...17H detection circuit, 12...Synchronization separation circuit, 13...17H extraction circuit, 14...Switching pulse generation circuit, 15...Clock regeneration circuit, 16 ……
D flip-flop, 17...Buffer amplifier, 1
8, 19...analog and gate, 20...inverter, 21...buffer amplifier, 24...
21H detection circuit, 25...1H memory, 26...NOR gate, 27...Gated oscillation circuit, 28...
...flipflop, 29...counter.

Claims (1)

[Claims] 1. Shaping and extraction means for waveform shaping and extracting a digital additional signal included in a specific horizontal period of a television signal, and a horizontal period that normally outputs the television signal and is different from the horizontal period in which the digital additional signal is included. A magnetic recording device comprising: switching means for switching and outputting the video signal of the horizontal period and the output of the shaping/extracting means; and magnetic recording means for magnetically recording the output of the switching means.