KR910007634Y1 - Dolby noise eraze type distinction and control circuit - Google Patents

Abstract

No content.

Description

Dolby Noise Canceling Tape Identification and Control Circuit

1 is a block diagram of the present invention.

2 is a circuit diagram of an embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

10: time setting unit 20: oscillation unit

30: Dolby control unit 40: Dolby and audio circuit

50: control signal generator 60: signal detector

The present invention relates to a control circuit of an audio device with a built-in DOLBY Noise Reduction circuit (hereinafter referred to as a Dolby circuit). It relates to a circuit for appropriately controlling.

In general, Dolby Circuit is a type of level control system developed by Dolby Laboratories in the UK. It reduces noise over the entire audio band by compressing the level at the input and increasing the level at the output.

In audio or video equipment that normally incorporates a Dolby circuit, if the Dolby function switch is in the "on" state, it is either a tape recorded in the Dolby circuit method or a tape recorded in a general manner without using the Dolby circuit method. Regardless, the Dolby Noise Canceling circuit is operated, so when the tape is not used in the Dolby method when recording, the Dolby method is used to play the Dolby method, resulting in the high band being de-emphasis. The drawback was that the audio signal would not play back as it was.

Therefore, an object of the present invention is to add a predetermined reference signal to a tape during recording in an audio device employing a Dolby circuit, and when the reference signal is detected during playback, a Dolby circuit is introduced and when the reference signal is not detected, a Dolby circuit is used. The present invention provides a control circuit that can operate as a general circuit.

Another object of the present invention is to provide a control circuit that can provide the sound faithful to the original sound with ease of use by being automatically controlled according to the state of the recorded tape when using the Dolby circuit.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of the present invention, which oscillates as much as the time set by the time setting unit 10 for setting a time when a predetermined reference signal is recorded on a tape at the time of recording, and outputs the oscillation output only for a predetermined time. An oscillation unit 20 to be applied, a Dolby and audio circuit unit 40 comprising a known Dolby circuit and an audio amplification circuit, a Dolby control unit 30 for controlling the operation of the Dolby circuit, and the time setting circuit at the beginning of recording ( When the signal generated by the oscillator 20 is recorded on the tape for the time set in 10), the signal detection unit 60 detects the signal during reproduction and converts the signal into a digital signal, and the reference of the initial recording in the signal detection unit 60. When a signal is detected, the control signal generator 50 generates a Dolby control signal according to the signal.

2 is a detailed circuit diagram of an embodiment according to the present invention, in which a portion consisting of transistors Q ₁ , Q ₆ , resistor R ₁ , R ₁₂ , capacitor C ₁ , and inverter 11 is shown. Corresponding to the time setting section 10, a portion composed of the transistors Q ₂ (Q ₃ ), the NAND gate 21, the inverter 23, the variable resistor VR ₁ , and the oscillation circuit 22 is an oscillation section ( 20 corresponds to the resistor R ₁₁ , the switch SW ₁ (SW ₂ ), the diode D ₁ (D ₂ ), the inverter 32, and the end gate 31. ), A part composed of a known Dolby circuit 41 and an audio signal amplifying circuit 42 corresponds to Dolby and an audio circuit 40, and a resistor (R ₄ ) (R ₅ ) (R ₁₀ ), a capacitor The portion composed of (C ₄ ) (C ₅ ), diode (D ₃ ) (D ₄ ), inverter (51) (52), and flip-flop (53) corresponds to the control signal generator (50), and resistor (R). ₂ ) (R ₃ ) (R ₆ -R ₉ ) (R ₁₃ ), condenser (C ₂ ) (C ₃ ) (C ₆ ), amplification buffer 61, inverter 62, comparator 63 and track The portion composed of the transistors Q ₄ -Q ₆ corresponds to the signal detection unit 60.

In the figure, reference numeral SW ₃ is a swing value controlled according to a user's recording / playback switch selection, and connects the head unit 70 and an audio circuit.

Therefore, the present invention will be described with reference to the above-described drawings and configurations.

If in the first recording during Dolby circuit "on / off" switch (SW _1), the on state C constituting the recording (REC) in accordance with the key depressing is applied to a prescribed "high" signal at the terminal 55 a differential circuit _4, Since it is differentiated by R ₄ , it becomes a predetermined pulse and is then inverted by the inverter 51 and applied to the set input terminal S of the flip-flop 53.

Accordingly, the output terminal Q of the flip-flop 53 is output "high" and is applied to one input terminal of the AND gate 31 through the diode D ₂ , and the switch SW ₁ is connected in the "ON" state. Therefore, since the "high" signal is applied to the other input terminal of the AND gate 31 through the resistor R ₁₁ , the output of the AND gate 31 becomes "high".

Therefore, the Dolby circuit 41 starts to operate by outputting the "high" signal of the AND gate 31.

The output signal of the AND gate 31 because the "low" signal to the base-side input terminal of the transistor (Q ₁₎ after being inverted by the inverter 11 is applied to the transistor (Q ₁₎ is turned "on" state R ₁ And a predetermined pulse by the time constant of C ₁ ) Is output to the transistor Q ₆ .

As a result, both input terminals of the NAND gate 21 are "high" and the output is "low". Therefore, the input terminal of the NAND gate 21 is input to the base terminal of the transistor Q ₂ , so that a predetermined power is applied to the oscillation circuit 22 to generate oscillation. Will be done.

On the other hand, in the inverter 23, the collector output signal of the transistor Q ₆ is inverted, that is, becomes a "low" signal, and the transistor Q ₃ is "on", and at this time, the switch SW ₃ is operated by the recording (REC) key operation. Is connected to the REC side, a predetermined reference signal is output to the head portion 70 and recorded on the tape.

Here, the output level of the oscillator 20 is adjusted in the same manner as the output level of the audio amplifier circuit 42 by the variable resistor VR ₁ .

Therefore, as described in the above-described process, the predetermined reference signal is taped through the head unit 70 through the oscillation unit 20 for a predetermined time set by the resistor R ₁ and the capacitor C ₁ of the time setting unit 10. It can be easily understood that it is recorded (or recorded) on the image.

On the other hand, when a predetermined " high " signal is applied from the terminal 56 as the PB key is pressed, it is differentiated from C ₅ and R ₅ to become a predetermined pulse and inverted by the inverter 52 to flip the flip-flop 53. Since it is input to the reset terminal R of, the "low" signal is output from the output terminal Q of the flip-flop. Since the signal picked up by the head unit 70 at the time of reproduction is a weak level, it is amplified by the amplification buffer 61, and then resistors R ₂ (R ₃ ) and capacitors C ₂ (C ₃ ). After filtering only the reference signal generated by the oscillator 20 by the comparator 63, the output signal is made into a rectangular pulse through the transistor Q ₄ and filled by the resistor R ₆ and the capacitor C ₆ . and discharge and the transistor (Q ₅₎ "turn-on / onpeu" as.

As a result, the power supply of the resistor R ₇ is maintained at 0.6 V or more, and the output of the transistor Q ₆ becomes "low".

At this time, the "low" signal is applied to the clock terminal CK of the flip-flop 53 at the falling edge of the output pulse and becomes "high" at the output terminal Q.

Thus, the AND gate 31 is output as "high" and the Dolby circuit function can be operated by applying the "high" signal to the Dolby circuit 41.

As described above, according to the present invention, when the audio device employing the Dolby circuit is used, the recorded tape automatically controls the use of the Dolby circuit during playback according to the use of the Dolby circuit. There is an advantage to providing.

Claims (1)

In an audio system provided with a known Dolby Noise Canceling circuit and an audio amplification circuit, a time setting section (10) for setting a time at which a predetermined reference signal is recorded on a tape at the time of recording, and the time setting section (10). An oscillation unit 20 for outputting a reference signal having a predetermined oscillation output to the head unit 70 only by oscillating for a predetermined time period, and a dolby controller 30 for controlling the operation of the dolby noise canceling circuit; A signal detector 60 for recording a reference signal output from the oscillator 20 for a time set by the time setting circuit 10 on a tape, detecting the signal during reproduction, converting the signal into a predetermined digital signal, and outputting the signal; Dolby job, characterized in that consisting of a control signal generator 50 for generating a Dolby circuit control signal according to the signal when the reference signal of the initial recording is detected by the signal detector 60 during playback Sound removal tape discrimination and control circuit.