KR920001145B1 - Automatic switching circuit for vtr - Google Patents

Abstract

The circuit is capable of shifting the selection between VHS brightness play-back and S-VHS brightness play-back in a video tape recorder. The circuit includes: a buffer (6) for buffering and amplifying FM signals; a gate (7) for passing the FM signals during a vertical synchronizing period; a frequency divider (8) for supplying vertical synchronizing signals; band pass filters (9) and (11) for passing the FM signals only between 3.4 MHz and 5.4 MHz; wave shaping sections (10) and (12) for shaping the passed frequencies into a dc voltage; a comparing section (13) for comparing the output of the wave shaping sections; and a flip-flop (14) for supplying switching control signals to an analogue switch (3).

Description

Automatic switching circuit during playback of video tape recorder

1 is a circuit diagram of the invention.

Figure 2a is a frequency spectrum state diagram of the VHS scheme.

2b is a frequency spectrum state diagram of the S-VHS scheme.

* Explanation of symbols for the main parts of the drawings

1: preamplifier 2: color signal reproducing system

3: analog switch 4: VHS luminance repro

5: S-VHS luminance reproduction system 6: beeper

7: gate 8: divider

10,12: detector 13: comparator

14 flip-flop 20: signal discrimination unit

The present invention provides a video tape recorder capable of VHS and S-VHS playback, wherein the video tape recorder is configured to determine a signal state recorded on a tape and to automatically switch the selection of a VHS luminance reproduction system and an S-VHS luminance reproduction system. It relates to an automatic switching circuit during regeneration.

There are two types of video-recording methods in the video tape recorder, the VHS method and the beta method.

However, in the VHS method, the interference between the luminance signal and the color signal is generated by recording and reproducing a composite video signal in which the luminance signal and the color signal are mixed.

Therefore, the S-VHS method (SUPPER-VIDEO HOME SYSTEM) was developed to compensate for the shortcomings of the VHS method, and the luminance and color signals were separated and recorded and reproduced to eliminate interference, but the VHS and S-VHS methods were obtained. Since there is incompatibility between the two, there is a need to select the VHS luminance reproduction system and the S-VHS luminance reproduction system by distinguishing the VHS system and the S-VHS system recorded on the video tape.

Conventionally, in order to distinguish the recording method of such a video tape, in the case of the S-VHS method, an S-VHS discrimination hole (HOLE) is formed on one side of a cassette in which the video tape is embedded, and then S is determined by a mechanical structure. -The S-VHS luminance regeneration system was selected according to the presence or absence of the VHS identification hole.

Therefore, the S-VHS video tape can be recorded on the S-VHS video tape with the S-VHS discriminant hole. However, the S-VHS luminance playback system is selected by the S-VHS discriminant hole during playback. The VHS signal cannot be reproduced.

The object of the present invention is to automatically reproduce the VHS luminance by judging the signal state recorded on the video tape without selecting the driving of the VHS luminance reproduction system and the S-VHS luminance reproduction system according to the presence or absence of the S-VHS determination hole as described above. It is possible to select the operation of the system and the S-VHS luminance regenerative system.The FM signal reproduced from the tape is detected during the vertical synchronization period, and then passed through two band pass filters having different bands, and then detected and compared respectively. The driving of the VHS luminance reproduction system and the S-VHS luminance reproduction system is automatically selected according to the comparison output.

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

The present invention applies the FM signal picked up from the head (HD) and amplified by the preamplifier (1) to the color signal reproducing system (2), and optionally via the analog switch (3) with the VHS luminance reproducing system (4). A VHS and S-VHS reproducible video tape recorder applied to an S-VHS luminance reproduction system (5), comprising: a buffer (6) for buffering and amplifying the FM signal output from the preamplifier (1), and the buffer ( A gate 7 for passing the FM signal of 6) during the vertical synchronization period, a divider 8 for applying a vertical synchronization signal to the gate 7 and supplying the vertical synchronization signal through four fields when a dropout occurs; A detector (10) (12) for detecting a pass frequency of a band pass filter (9) (11) for passing the FM signal passing through the gate (7) only in the 3.4 MHz and 5.4 MHz bands; Comparator 13 for comparing the output voltages of the detectors 10 and 12 and the detectors 10 and 12, and the comparator 13 To trigger the output to a vertical synchronization signal delayed by the delay unit 15 which will configure the flip-flop 14 in the signal identification unit 20, for supplying a switching control signal of the analog switch 3.

The effects of the present invention configured as described above will be described. The FM signal picked up by the head HD and amplified by the preamplifier 1 is applied to the color signal reproducing system 2, the analog switch 3, and the signal discriminating unit 20, and the excitation signal discriminating unit 20. Is applied to the analog switch 3 as a switching control signal as 'high level' for a tape recorded in the VHS method and 'low level' for a tape recorded in the S-VHS method according to the operation to be described below. The VHS luminance reproduction system 4 is selected in the case of a tape recorded in the VHS system, and the S-VHS luminance reproduction system 5 is selected in the case of a tape recorded in the S-VHS system.

Therefore, the VHS luminance reproduction system 4 and the S-VHS luminance reproduction system 5 are selected in accordance with the manner recorded on the tape. Hereinafter, an operation of the signal discrimination unit 20 outputting different switching control signals according to the tape recording method will be described. The FM signal amplified by the preamplifier 1 is buffered and amplified in the buffer 6 and then passed through the gate 7 to be conductive during the vertical synchronization period.

Here, the divider 8 applying the vertical synchronization signal to the gate 7 conducts the gate 7 by applying the vertical synchronization signal to the gate 7 during the vertical synchronization period, but if a drop out occurs. 4 vertical sync signals are applied to the gate 7 without being applied to the gate 7 until 4 vertical sync signals are applied (4 fields pass) after being cleared by the drop-out pulse DO. The stable vertical synchronizing signal is applied to the gate 7.

The FM signal passing through the gate 7 passes through the 3.4 MHz band pass filter 9 and the 5.4 MHz band pass filter 11 and is applied to the detectors 10 and 12 to be detected at the DC level. In this case, when the tape recorded in the VHS method is played back, the FM signal is 3.4 MHz as shown in FIG. 2a, and when the tape recorded in the S-VHS method is played back, the FM signal is displayed in the main modulation carrier 5.4 as shown in FIG. MHz.

Therefore, when the tape recorded in the VHS method is reproduced, the DC voltage detected by the detectors 10 and 12 through the band pass filters 9 and 11 is higher in the detector 10 and the S-VHS method. When the recorded tape is reproduced, the detector 12 becomes higher in the DC voltage detected by the detectors 10 and 12 through the band filters 9 and 11.

Therefore, the output of the comparator 13 comparing the outputs of the detectors 10 and 12 outputs a high level when the tape is recorded in the VHS method and a low level when the tape is recorded in the S-VHS method. It is applied to the input terminal D of (14).

In this case, a time delayed vertical synchronization signal is applied to the clock terminal of the flip-flop 14 to output the output of the input terminal D to the output terminal Q at the positive edge pulse of the vertical synchronization signal. .

Therefore, the output terminal Q of the flip-flop 14 outputs a high level when the tape is recorded by the VHS method and a low level when the tape is recorded by the S-VHS method. The output of the flip-flop 14 is output. The output of the terminal Q is applied to the switching control signal of the analog switch 3, so that when the tape is recorded in the VHS method, the FM signal is applied to the VHS luminance reproducing system 4, and the signal is processed. When the recorded tape is reproduced, it is applied to the S-VHS luminance reproduction system 5 for signal processing.

Therefore, it is possible to automatically select the driving of the VHS luminance reproduction system 4 and the S-VHS luminance reproduction system 5 without configuring the S-VHS determination hole in the tape cassette. On the other hand, in a multi-video tape recorder capable of reproducing PAL and NTSC in a VHS VTR, the FM signal is automatically switched if only the band pass frequency of the band pass filter 9 or 11 is changed.

As described above, in the video tape recorder capable of VHS and S-VHS playback, the VHS luminance system and the S-VHS luminance system can be automatically selected according to the signal state recorded on the video tape. This eliminates the need to construct holes for discriminating S-VHS in conventional and simple video cassettes, and enables the playback of signals recorded in VHS format on S-VHS tapes with compatibility.

Claims (1)

The FM signal picked up by the head HD and amplified by the preamplifier 1 is applied to the color signal reproducing system 2 while the VHS luminance reproducing system 4 and the S-VHS are selectively supplied via the analog switch 3. A VHS and S-VHS reproducible video tape recorder applied to a luminance reproduction system (5), comprising: a buffer (6) for circularly amplifying the FM signal output from the preamplifier (1), and the buffer (6) A gate 7 for passing the FM signal during the vertical synchronization period, a divider 8 for applying a vertical synchronization signal to the gate 7 and supplying a vertical synchronization signal through four fields when a dropout occurs, and the gate A band pass filter (9) (11) for passing the FM signal passing through (7) only in the 3.4 MHz and 5.4 MHz bands; and a detector for detecting a pass frequency of the band pass filters (9) and (11) with a DC voltage. (10) 12, the comparator 13 for comparing the output voltages of the detectors 10 and 12, and the output of the comparator 13 Video tape, characterized in that the signal discriminating unit 20 is constituted by a flip-flop 14 which is triggered by a vertical synchronizing signal delayed by the delay unit 15 and supplied as a switching control signal of the analog switch 3. Automatic switching circuit during record playback.

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