KR940000982B1 - Hi-fi signal and normal signal automatic switching apparatus of hi-fi vcr - Google Patents

Abstract

The apparatus for switching between the HIFI mode and the normal mode in HIFI VCR comprises a dropout detector for generating dropout pulse, a switch controlled by the pulse, an envelope detector for detecting envelope of the output of a bandpass filter by control of the switch, a system controller for selecting HIFI mode or normal mode by envelope pulse, and an audio output means for outputting HIFI or normal mode selectively from an attenuation circuit by control of a system controller. Thus this invention obtains high fidelity sound regardless of any damage to the video tape.

Description

Hi-Fi normal automatic switching device of Hi-Fi VCR

1 is a reference diagram of a sound output system in a conventional hi-fi VCR.

2 is a reference diagram of a sound output system of a hi-fi VCR equipped with a hi-fi normal automatic switching unit according to the present invention.

3 is a waveform diagram showing an image RF waveform and a switching pulse, (b) is a reference diagram of an envelope waveform related to the present invention, and (c) is an operation waveform diagram of each part of FIG.

* Explanation of symbols for main parts of the drawings

11: envelope detector 12: switch device

13: dropout detector 14: system controller

15: Audio output controller

The present invention relates to a VCR having a HIFI sound reproducing function, which is particularly useful when playing a high fidelity tape in such a VCR, so that audio output noise or system muting can be eliminated at a portion where the tape is damaged. It relates to a normal automatic switching device. The conventional VCR that made hi-fi tape reproducible shows the sound system as shown in FIG.

Here, left and right stereo audio head drums 21 and 22, preamps 23 and 24, signal mixers 25, headswitching pulse generators 26, bandpasses 27 and 33 and demodulators. (28, 34), sample and holders (30, 36), noise dampers (31, 37), dropout detectors (29, 35), and the like.

In the VCR, the signals reproduced by the left and right audio head drums 21 and 22 are amplified through the preamps 23 and 24, which are left and right heads according to the output of the head switching pulse generator 26. The sum of the outputs is a continuous signal, and this output is obtained through left and right channel signals through the band pass channels 27 and 33, respectively, and then demodulated through the demodulators 28 and 34. The out detectors 29 and 35 detect this and mute the FM wave. However, in such a prior art, if there is damage to the tape during playback, it is detected by the drop out detectors 29 and 35, resulting in inconvenience in using the system. In addition, even if it is not muted in the damaged portion of the tape, it causes noise to cause an unpleasant listening feeling when listening to high-quality hi-fi sound.

An object of the present invention was developed to improve the problems of the prior art as described above, by the automatic switching of high-fidelity sound to normal sound in the tape damage unit as described above, the ease of use of such a system is increased and high quality VCR It is possible to provide.

The present invention particularly provides a dropout detector for generating a dropout pulse for a damaged part of the tape, a switch device for switching the audio envelope detector to the output of the dropout detector, and a hi-fi and normal output in a system controller. An audio envelope detector with an audio envelope pulse generation capable of obtaining an audio envelope, an audio output controller for selectively switching and controlling the audio output in a hi-fi and normal state, and a system controller for controlling the audio output controller. It features a normal automatic switching device.

This will be described in more detail below. That is, Figure 2 shows the sound system of a hi-fi VCR equipped with a hi-fi normal automatic switching device according to the present invention.

Here, at the output of the band pass 27 and 33 of the left and right channels, an audio envelope detector 11 is connected, in which the system controller 14 detects audio envelope pulses that enable signal discrimination between hi-fi and normal states. A switching device 12 for switching the envelope detector 11 in accordance with the detection of the damaged part of the tape, a dropout detector 13 for providing the switching device 12 with a switching pulse in response to the detection of the tape damaged part; It is connected between the system controller 14 which controls the audio output controller 15 and the normal noise attenuators 31 and 37 according to the detection of the tape damage part, and selectively switches the left and right outputs and the normal output of the stereo hi-fi. And an audio output controller 15 for outputting. The present invention of such a configuration is as follows.

As in normal operation, signals reproduced and read by the left and right audio head drums 21 and 22 are passed through the preamplifiers 23 and 24 and the signal mixer 25, and the sound RF waveforms as shown in a of FIG. Create This RF signal is applied to the demodulators 28 and 34 via bandpasses 27 and 33 of 1.3 MHz and 1.7 MHz, respectively, while c in Fig. 3 (b) of the audio envelope detector 11 is used. Create an audio envelope waveform such as This audio envelope waveform is sent to the system controller 14 to generate a hi-fi / normal pulse for control of the audio output controller 15. At this time, the output condition of the system controller 14 is hi-fi when the audio envelope pulse is logic 1, and normal when logic Φ. The hi-fi / normal stage (H / N) generates logic Φ when hi-fi and logic 1 when normal. .

On the other hand, in the part where the tape is damaged during the playback process of the tape, the image RF becomes like the x part in e of FIG. 3 (c), which is detected by the dropout detector 13 and Generates a pulse like h).

The pulse generated by the dropout detector 13 is provided to the switch device 12 so that when the switch device 12 is turned on, the audio envelope pulse becomes a pulse equal to g of FIG. At this time, in the system controller 14, the hi-fi normal stage H / N becomes a logic Φ, and the audio output controller 15 generates an output in the normal state as i of FIG. In addition, when the damaged part is left out, it returns to the normal state again and the audio output controller 15 generates stereo hi-fi output of left and right outputs.

The present invention is advantageous in that it is possible to provide high-quality sound and convenience of using such a system since the discomfort of audio listening due to muting or noise is not caused even if the tape is damaged in the hi-fi VCR.

Claims (1)

In the Hi-Fi VCR, a dropout detector 13 for generating a dropout pulse at a damaged area of the tape, a switch device 12 for switching to an output of the dropout detector 13, and the switch device ( 12), the envelope detector 11 detects the envelope pulse at the output of the bandpass and sends it to the system controller 14 and the left and right stereo hi-fi signals or normal according to the output of the envelope detector 11; A system controller 14 for generating a signal output for selecting a signal, and outputs the left and right stereo hi-fi signals and the normal signal selectively from the outputs of the noise dampers 31 and 37, following the output of the system controller 14; A hi-fi normal automatic switching device of a hi-fi VCR provided with an audio output controller (15).