JPH01154363A - Recording mode discriminating device - Google Patents

Abstract

PURPOSE:To stabilize a recording and reproducing system so that the system can be constituted of ICs easily by discriminating a difference in recording mode in accordance with a difference in frequency of FM signals recorded on a recording medium by means of a mode detecting section and connecting an output terminal with a constant-voltage source or the mode detecting section by means of a switching circuit depending upon a discriminated result. CONSTITUTION:FM signals are inputted to a reproducing amplifier section 2 from the input terminal 1 of the recording and reproducing mode discriminating device of a video signal recorder and reproducing device and the signals are amplified. The output signal of the amplifier 2 is inputted to a recording mode detecting section 3 and envelope detecting section 4 and the recording mode set in accordance with the frequency allocation of the reproduced FM signals is discriminated at the mode detecting section 3. Moreover, at the envelope detecting section 4 whether the FM signals are existing signals or nonexisting signals is discriminated and a control signal is inputted to a switching circuit 5. Then the circuit 5 is controlled by means of the control signal of the detecting section 4 and an output terminal 6 is connected with a constant-voltage source 7 during the nonexisting period (c) of the FM signals and with the mode detecting section 3 during the existing periods (a) and (b). Thus the FM signals are outputted by discriminating the recording mode.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a recording mode determining device for a video signal recording and reproducing apparatus that records and reproduces video signals on a recording medium such as a magnetic tape.

2. Description of the Related Art In recent years, with the spread of television broadcasting, video tape recorders, video discs, etc., there has been an increasing demand for higher quality video information media. Even in home VTRs (abbreviation for video tape recorders), the S/N ratio and resolution have already been improved by increasing the FM recording frequency of video signals to a higher band.

Problems to be Solved by the Invention Changing the allocation of high frequencies due to high banding may result in loss of compatibility with conventional formats, and there may be cases where multiple formats can be recorded on a recording medium of the same shape. , it becomes necessary to determine the recording format from the reproduced signal. For this reason, a recording mode detection section is provided in the recording/reproducing apparatus. However, at this time, a no-signal period in which there is no FM signal may occur between recorded formats or even between the same formats.

FIG. 2 shows FM signal waveforms between each format. As this waveform shows, there is a no-signal period cl in which there is no output imaging range between waveform a of format I and waveform 2 of format
: When the recording mode is discriminated, it becomes impossible to detect the recording format, and the discrimination output becomes unstable.

An object of the present invention is to fix the discrimination output to a certain mode and provide a stable discrimination output in order to stabilize the recording/reproduction system during a period in which recording mode discrimination is impossible.

Means for Solving the Problems The recording mode discrimination device of the present invention includes a recording mode detection section that discriminates the recording mode based on the difference in frequency allocation of the FM signal recorded on the recording medium, and a recording mode detection section that detects no signal of the FM signal. and a switching circuit that connects the output terminal to a constant voltage source when the FM signal is absent and to the recording mode detector when the FM signal is present, according to a control signal from the envelope detector. be.

According to the recording mode discriminating device of the present invention, when the FM signal is present, the recording mode is determined and output, and when the FM signal has no output amplitude and there is no signal, a fixed mode is output.

Embodiment An embodiment of the recording mode discriminating device of the present invention will be described with reference to the block diagram shown in FIG.

An input terminal 1 is connected to a reproduction amplifier section 2, and a reproduction FM signal is inputted from the input terminal 1 to the reproduction amplifier section 2 and amplified. The output terminal of the reproducing amplifier 2 is connected to the recording mode detecting section 3 and the envelope detecting section 4, and the output signal from the reproducing amplifier section 2 is input to the recording mode detecting section 3 and the envelope detecting section 4. The recording mode detection unit 3 determines the recording mode based on the difference in frequency allocation of the reproduced FM signal. On the other hand, the envelope detection section 4 determines whether the reproduced FM signal has a signal or no signal, and a control signal is thereby inputted to the switching circuit 5. In the switching circuit, the output terminal 6 is connected to the constant voltage source 7 during the no-signal period.
A certain DC voltage is output from the output terminal 6 as a certain fixed mode.

In addition, during the signal period, the output terminal 6 is connected to the recording mode detection unit 3.
and outputs an output signal in which the recording mode is determined.

Effects of the Invention According to the present invention, the recording and reproducing system can be stabilized by providing a discrimination output fixed to a certain mode during a no-signal period when a reproduced FM signal is missing. Further, the present invention has the advantage that the circuit configuration is simple and that it can be easily integrated into a circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the recording mode discriminating device of the present invention, and FIG. 2 is an FM signal waveform diagram for explaining the problem to be solved by the present invention. 1... Input terminal, 2... Playback amplifier section, 3... Recording mode detection section, 4... Envelope detection section, 5...・Switching circuit,
6... Output terminal, 7... Constant voltage source. Name of agent: Patent attorney Toshio Nakao and one other person t・-Yoko Hitokata 7-・Constant voltage source 4' Figure 2. 0. -Format I East b-・Formacito■ Hirosugi (=-#!, signal period

Claims (1)

[Claims] A recording mode detection section that determines the recording mode based on the difference in frequency allocation of the FM signal recorded on the recording medium, an envelope detection section that detects no signal of the FM signal, and an output terminal according to a control signal from the envelope detection section. A recording mode discriminating device comprising: a switching circuit that connects the FM signal to a constant voltage source during a period when there is no signal, and connects the FM signal to the recording mode detecting section during a period when a signal is present.