Dynamic magnetic information storage or retrieval – Monitoring or testing the progress of recording
Patent
1988-06-28
1990-08-14
McElheny, Jr., Donald
Dynamic magnetic information storage or retrieval
Monitoring or testing the progress of recording
360 69, H04N 578
Patent
active
049491954
DESCRIPTION:
BRIEF SUMMARY
FIELD OF TECHNOLOGY
The present invention relates to the discrimination of an FM carrier frequency in a video signal magnetic recording and/or reproducing apparatus (hereinafter referred to as VCR).
BACKGROUND ART
FIG. 3 illustrates a frequency allocation for the standard mode described in a handling manual of, for example, the VCR of Sony make, HF-900 (hereinafter referred to as the conventional apparatus), wherein 1 represents a luminance signal FM wave, 2 represents a low frequency range conversion chroma signal, 3 represents an FM carrier frequency (3.6 MHz) of a sync signal tip, and 4 represents an FM carrier wave (4.8 MHz) of a white peak. FIG. 4 illustrates a frequency allocation of a high band mode, wherein 1a represents a luminance signal FM wave of the high band mode, 3a represents an FM carrier frequency (4.4 MHz) of a sync signal tip, and 4a represents an FM carrier frequency (5.6 MHz) of a white peak.
In the above described conventional apparatus, according to the standard mode, at the luminance signal FM wave 1, the FM carrier frequency 3 of the sync signal tip is 3.6 MHz, and the FM carrier frequency 4 of the white peak is 4.8 MHz. On the other hand, according to the high band mode, the FM carrier frequency 3a of the sync signal tip is 4.4 MHz and the FM carrier frequency 4a of the white peak is 5.6 MHz.
Although in the VCR the frequency characteristics of the FM wave must be modified where the carrier frequency of the luminance signal FM wave is to be changed, the conventional apparatus is so designed that the frequency characteristics of the reproduced FM wave are modified by verifying a reproduced image on a monitor TV with sight and then by manually operating a change-over switch. Accordingly, it may happen that at the high band mode the change-over switch may be connected to the standard mode position, and in that case, there has been a problem in that the reproduced image tends to be disturbed.
SUMMARY OF THE INVENTION
The present invention has been developed with a view to eliminating the above discussed problem and has for its object to provide a video signal magnetic recording and/or reproducing apparatus which is able to automatically discriminate the high band mode and to then automatically switch the mode over during reproduction.
The VCR to which the present invention pertains is one which is provided with a bandpass filter capable of allowing to pass therethrough only a frequency in the vicinity of a tip of a synchronizing signal of the luminance signal FM wave modulated by a carrier of predetermined frequency, a wave detecting circuit for carrying out an envelope wave detection of an output from the filter, and a discriminating circuit for discriminating the high band mode in reference to an output from the wave detecting circuit.
In the present invention, the discrimination is carried out by the bandpass filter through which only the frequencies in the neighborhood of the sync signal tip portion of the luminance signal FM wave can pass, and the high band mode can be discriminated by the envelope wave detection of a signal which has passed.
According to the present invention, since the discrimination of the high band mode is carried out by means of the bandpass filter through which only the frequencies in the neighborhood of the tip of the synchronizing signal of the luminance signal FM wave can pass, and then by effecting the envelope detection of the signal which has passed therethrough, there are such effects that a highly precise mode discrimination can be accomplished with the simple and inexpensive apparatus and by the utilization of the result of such mode discrimination the mode change-over can be carried out automatically.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein:
FIG. 1 is a block circuit diagram illustrating a constructio
REFERENCES:
patent: 4240102 (1980-12-01), Groeneweg
patent: 4574301 (1986-03-01), Sachs
patent: 4604659 (1986-08-01), Itoh et al.
patent: 4722004 (1988-01-01), Miyamoto et al.
patent: 4811122 (1989-03-01), Kido et al.
McElheny Jr. Donald
Mitsubishi Denki & Kabushiki Kaisha
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