KR910008977Y1 - Fm stereo recording circuit for 8mm vtr - Google Patents

Abstract

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Description

8mm VTR FM Stereo Recording Circuit

1 is a circuit diagram of the present invention.

FIG. 2a is a frequency distribution diagram of a typical 8mm VTR recording, and FIG. 2b is a frequency distribution diagram of FM stereo recording.

* Explanation of symbols for the main parts of the drawings

1: sink separation unit 2: separation circuit

3: luminance processing unit 4: chromaticity processing unit

5: video signal processor 6: audio processor

10: audio channel switching circuit 15: video signal determination unit

20: electronic switch C1, C2, C3: capacitor

The present invention relates to an 8-mm VTR FM stereo recording circuit capable of recording an FM stereo signal using an 8-mm VTR (video tape recorder) system.

Unlike conventional VTRs, the 8-mm VTR recording method differs from conventional VTRs in that the audio signal is FM-modulated (1.5MHz) and recorded on the video track of the tape along with luminance and chroma signals and servo ATF (Auto Track Finding). It appeared as in Figure 2a.

Therefore, in the 8-mm VTR, there was only one audio carrier signal (AFM), so it could not be recorded in stereo but only mono sound.

In the 8 mm VTR, the audio signal is recorded together with the video signal, so without the video signal, it is impossible to synchronize the audio signal.

In view of the above, the present invention aims to record only mono sound when recording an audio signal such as a video signal at 8 mm VTR, and to record only an audio signal without a video signal. A circuit capable of recording FM stereo signals in the absence of a video signal by allowing the left and right audio carrier signals to be symmetrically recorded using a pseudo synchronization signal using a frequency range corresponding to a color and luminance signal of a band. It detects the vertical sync signal in the video signal and detects the presence of the video signal, and if there is no video signal, applies a pseudo vertical sync signal to the drum servo and controls the audio processor to control the audio processor frequency. To be recorded from

This will be described in detail with reference to the accompanying drawings.

The sync signal of the video signal is separated from the sink separating unit 1 and applied to the drum servo, while the separating circuit 2 separates the luminance and chroma signal from the video signal to the luminance processing unit 3 and the chroma processing unit 4. A signal processor 5, a signal processor 20 for mixing the luminance and chroma signals of the luminance processor 3 and the chroma processor 4 with the audio carrier frequency of the audio processor 6 and applying them to the recording amplifier 8 In the VTR, the video signal determining unit 15 which separates and smoothes the vertical synchronizing signal in the video signal and outputs a video signal presence / absence determination signal, and is switched to the determination signal of the video signal determining unit 15, and is synchronized with the synchronization separating unit. (1) and an electronic time switch (SW1) for selectively applying a pseudo synchronizing signal to the drum surrogate, and the video signal determination unit (15) is driven by the determination signal and is a sub audio of the audio processing unit (6). It is composed of the audio channel switching circuit 10 for controlling the carrier frequency of the supply.

That is, in the present invention, the video signal inputted to the terminal 18 is applied to the transistor Q1 to which the coupling capacitor C1 and the bias resistors R1 and R2 are connected to separate the vertical synchronization signal, and the separated vertical signal. The video signal determining unit 15 is configured to smooth the synchronizing signal with the condenser C2 so that the composition of the transistor Q2 is selected, and the electronic switch SW1 is switched to the output of the video signal determining unit 15 to generate a pseudo synchronizing signal. And a synchronizing signal of the sink separating unit 1 is selectively supplied to the drum servo of the terminal 12.

The output of the video signal determination unit 15 controls the driving of the transistors Q3 and Q4, and controls the output of the main audio carrier frequency and the sub audio carrier frequency of the audio processor 6, and the audio processor 6. The audio carrier frequency and the luminance and chromaticity signals of the luminance and chromaticity processing units 3 and 4 are synthesized together with the sub signal through the variable resistors VR1-VR4, the capacitors C4-C8, and the resistors R12-R16. After that, the signal processing unit 20 is configured to output the recording amplifier of the terminal 11 through the transistor Q5 driven by the recording signal.

In the present invention having such a configuration, the video signal input to the terminal 18 is applied to the base of the transistor Q1 through the DC blocking coupling capacitor C1, and at this time, the resistor R1 connected to the base of the transistor Q1. , R2 is set to detect only the vertical synchronization signal, so that the transistor Q1 is turned on in the vertical synchronization signal to detect the vertical synchronization signal.

The vertical synchronization signal detected by the transistor Q1 is smoothed by the capacitor C2 to 'turn on' the transistor Q2.

Accordingly, in the video signal determination unit 15, when the video signal is present, the transistor Q2 is 'tinned' to output a low level. When there is no video signal, the transistor Q2 is 'turned off' because no vertical synchronization signal is detected. 'Output high level.

The output of the video signal determination unit 15 is applied as a control signal of the electronic switch SW1 and the electronic switch SW1 outputs a high level (when there is no video signal) from the video signal determination unit 15. If it is connected to (a) and outputs a low level (if there is a video signal), it is connected to terminal (b).

Therefore, in the drum servo of the terminal 12, if there is a video signal, the synchronization signal separated by the sink separation unit 1 is applied, and if there is no video signal, the pseudo synchronization signal applied from the terminal 17 is applied. Drum servos can be synchronized with or without a video signal.

On the other hand, the video signal input to the terminal 18 is applied to the separation circuit 2 and separated into luminance and chroma signals, and then applied to the luminance processing unit 3 and the chroma processing unit 4 for signal processing, and then the signal processing unit 20 ) Is applied.

The audio processor 6 FM-modulates the left (L) and right (R) channel audio signals input to the terminals 7 and 8 by the oscillation frequencies of the oscillators VCO1 and VCO2, and the main audio carriers. The frequency and the sub audio carrier frequency are applied to the signal processing unit 20. At this time, the sub audio carrier frequency generated by the audio processing unit 6 is blocked from being supplied to the signal storage unit 20 according to the driving of the transistor Q4. do.

That is, when the transistor Q4 is 'turned on', the sub audio carrier frequency of the audio processor 6 may not be applied to the signal processor 20, and the sub audio carrier frequency may be changed only when the transistor Q4 is 'turned off'. 20).

In this case, the transistor Q4 is operated according to the driving of the transistor Q3 and the transistor Q3 is controlled by the output of the video signal determining unit 15, so that the output of the video signal determining unit 15 is high. At the level (when there is no video signal), the transistors Q3 and Q4 are 'turned off' so that the sub audio carrier frequency of the audio processing unit 6 is supplied to the signal processing unit 20 and the video signal determination unit 15 is provided. When the output of the low level (when there is a video signal), the transistors Q3 and Q4 are 'turned on' so that the sub audio carrier frequency of the audio processor 6 is not supplied to the signal processor 20.

Meanwhile, the sync signal, the luminance and chroma signal, the audio carrier frequency, and the servo ATF signal are synthesized by the transistor Q5 of the signal processor 20, and then applied to the recording amplifier of the terminal 11 to be recorded. The transistor Q5 of 20 is 'tinned' during recording by the signal applied at the high level at the time of recording to synthesize the emitter side signal and output it to the collector axis.

Here, capacitors C4-C8 are coupling capacitors, resistors R8-R11 are bias resistors, variable resistors TR1-VR4 are volumes for adjusting the recording signal current, and resistors R13-R16 are protective resistors.

That is, when there is a video signal, the video signal determination unit 15 outputs a low level and connects the electronic switch SW1 to the terminal L to apply the sync signal of the sink separation unit 2 to the drum servo, while the transistor By turning on (Q3) and (Q4) and applying only the main audio carrier frequency to the signal processing unit 20 in the audio processing unit 6, the audio signal recorded in the signal processing unit 20 is recorded only in the left channel so that the mono signal is recorded. do. In this case, the frequency distribution diagram is shown in FIG. 2A.

However, when there is no video signal, the video determination unit 15 outputs a high level and connects the electronic switch SW1 to the terminal a to apply a pseudo synchronizing signal to the drum servo, while transistors Q3 and Q4. The audio signal recorded in the signal processor 20 is a stereo signal of the left and right channels by 'turning off' and applying the sub audio carrier frequency to the signal processor 20 together with the main audio carrier frequency in the audio processor 6. do.

The frequency distribution diagram at this time is shown in FIG. 2B and the sub audio carrier frequency is recorded at the place where the chroma signal is recorded.

This allows audio signals to be recorded in stereo when there is no video signal at 8mm VTR.

As described above, the present invention allows only the main audio carrier to be recorded when there is a video signal and the sub audio carrier to be recorded in the chromaticity signal band when there is no video signal, while synchronizing the drum servo with a pseudo synchronization signal. In other words, it is possible to record stereo sound using 8mm VTR.

Claims (1)

A sync signal separation unit 1 and a video signal processing unit 5 for processing the synchronization signal of the video signal and the brightness and chroma signal in the luminance and chroma processing units 3 and 4, and the synchronization signal of the video signal processing unit 5 In the 8 mm VTR in which the signal processing unit 20 for mixing the luminance and chroma signal and the audio carrier frequency and the servo ATF signal of the audio processing unit 6 in the transistor Q5 and outputting it to the recording amplifier, The video signal determination unit 15 is provided with a video signal determination unit 15 for separating the synchronous signal into the transistor Q1 and smoothing the separated vertical synchronous signal with the capacitor C2 to control the driving of the transistor Q2. And an electronic switch SW1 for selecting and synchronizing the sync signal and the pseudo sync signal of the sink separating unit 1 to the drum sub-output as the output of the transistors. The outputs of the video signal determination unit 15 are transistors Q3 and Q4. ) And an audio channel switching circuit 10 for controlling the driving of the sub audio carrier frequency output applied from the audio processing unit 6 to the signal processing unit 20 according to the driving of the transistors Q3 and Q4. FM stereo recording circuit of 8mm VTR characterized in that it became.