JPS6215922B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a muting device, and is particularly applicable to a switching device, such as a tape recorder, in which a mechanical mechanism is driven by operation of an operating section, and a changeover switch is switched by the mechanical mechanism. It is an object of the present invention to provide a suitable mutating device.

On a tape recorder, the record button, playback button,
It is equipped with many operation parts such as a stop button. However,
When operating each operating section, there is a risk that switching noise may occur, so it is usually necessary to perform muting for a predetermined period of time after the operation of the operating section is started. The period during which the mutating is performed is
If it is short, noise will occur, and if it is long, the sound generation will be delayed, so it must be set to an appropriate value. on the other hand,
The operation of the operation buttons of a tape recorder involves switching of various changeover switches. For example, the stop button is used to stop the mechanical mechanism of a tape recorder, and the period from the start of operation until the mechanical mechanism switches and stops is relatively short, but the record button and playback button This operation switches the mechanical mechanism to a designated state and also involves switching electrical circuits such as a recording equalizer circuit and a reproduction equalizer circuit, so it takes additional time for the electrical circuits to stabilize. Therefore, when operating an operating section that does not involve switching an electrical circuit, such as a stop button, a relatively short period of muting is required, and when operating an operating section that involves switching an electrical circuit, such as a record button, a relatively short amount of muting is required. There is a need for a mutating device with variable muting time that can perform long muting.

The present invention has been made in view of the above points, and will be described below based on embodiments with reference to the drawings.

FIG. 1 is a circuit diagram showing a case where the muting device according to the present invention is applied to a tape recorder.
2 is a front stage amplifier, 2 is a main amplifier, 3 is a drive motor for the tape recorder, 4 is a battery as a power source, 5 is a mechanical mechanism of the tape recorder driven by the front drive motor 3, and 6 is a tape recorder drive motor. A trigger switch 7 closes when an operation button (not shown) starts operating, and a motor switch 7 that operates in conjunction with the trigger switch 6 when an operation button other than the stop operation button is operated and maintains the closed state unless released. , 8 is an R-S flip-flop circuit having a set input terminal S, a reset input terminal R, and an inverted output terminal; 9 is a positive input terminal to which a reference voltage is applied; a negative input terminal to which an input signal is applied; R
A first comparison circuit 10 connected to the set terminal S of the -S flip-flop circuit 8 has a reference voltage applied to its negative input terminal, an input signal applied to its positive input terminal, and an output terminal connected to the set terminal S of the R-S flip-flop circuit 8. 11, 12 and 13 are first, second and third bias resistors for supplying bias to the first and second comparison circuits 9 and 10; 13 is a second comparison circuit connected to the reset input terminal R of the circuit; Inverter, 1
4 is a switching transistor whose base is connected to the inverting output terminal of the flip-flop circuit 8 via the inverter 13 and the resistor 15;
is a shorting transistor whose base is connected to the inverting output terminal via a resistor 17; 18 is a capacitor shorted by the collector-emitter path of the shorting transistor 16; 19 is switched by the mechanical mechanism of the tape recorder a detection switch for detecting the end of operation of the circuit changeover switch, 2
0 is a control transistor that becomes conductive when the trigger switch 6 is closed and applies a trigger signal to the first comparator circuit 9.

Here, the operation of the tape recorder will be briefly explained. When an operation button for starting an operation, such as a record button or a playback button, is operated, the trigger switch 6 and the motor switch 7 are closed, and the drive motor 3 starts rotating. Since the trigger switch 6 is of an automatic return type, it will be automatically opened once it is closed, but the motor switch 7 will remain closed unless it is forcibly released, so the drive motor 3 will not rotate. sustain. Thus, the drive motor 3 drives the mechanical mechanism 5 through its initial rotation, and brings the tape recorder into a state corresponding to the operated operation button. Further, the mechanical mechanism 5 includes an electric circuit of a tape recorder,
For example, a recording/playback switch (not shown) for switching the recording equalizer circuit, playback equalizer circuit, etc.
Since the mechanical mechanism 5 has a switching function, when the mechanical mechanism 5 is in a state corresponding to the operated operation button, the electric circuit is also in the corresponding state. At that time, the detection switch 19 that detects the end of the switching operation is switched in accordance with the previous recording/re-switching switch, and is located at the position shown by the solid line when the playback button is pressed, and located at the position shown by the dotted line when the record button is pressed. However, by using a switching type switch, instantaneous
The terminal 19a can be grounded.

On the other hand, when an operation button that does not require a subsequent operation, such as a stop button, is pressed, the motor switch 7 is opened and the trigger switch 6 is closed for a short time. Therefore, the drive motor 3 stops after driving the mechanical mechanism 5 to a stopped state.

Next, the operation of the muting circuit will be explained. The muting circuit in a tape recorder eliminates the switching noise that occurs when operating the operation buttons,
It is also necessary to prevent the generation of noise during transient periods until the switched electrical circuit stabilizes.

If the tape recorder is now in a stopped state, the trigger switch 6 and motor switch 7 are in an open state, and the drive motor 3 is stopped. Therefore, the control transistor 20 is in an off state,
No set input is applied from the first comparator circuit 9 to the set input terminal S of the R-S flip-flop circuit 8, and the inverted output terminal is "H". Therefore, the discharge transistor 16 is on and the switching transistor 14 is off. The capacitor 18 is in a completely discharged state. At that time, the detection switch 19 is assumed to be in the position indicated by the solid line in the figure.

In this state, when the regeneration button is pressed at time A, the trigger switch 6 and motor switch 7 are closed, the drive motor 3 rotates, and the mechanical mechanism 5 enters the regeneration state. On the other hand, when the trigger switch 6 is closed and then automatically reset, a positive pulse shown in FIG. 2A is applied to the base of the control transistor 20, and the collector voltage of the control transistor 20 increases as shown in FIG. , becomes "L" for a short time. By properly setting the bias using the first to third resistors 11 to 13, when the collector voltage of the control transistor 20 becomes "L" for a short time, the output signal of the first comparison circuit 9 becomes "H" for a short time. , the "H" signal is applied to the set input terminal S of the R-S flip-flop circuit 8, and the inverted output terminal becomes "L" as shown in FIG. 2C. Therefore, the switching transistor 14 is turned on, the input terminal of the main amplifier 2 is grounded and muting is started, and at the same time the shorting transistor 16 is turned off and charging of the capacitor 18 is started.
The capacitor 18 is charged by the battery 4 through the resistor 21, and the voltage across it gradually increases as shown in FIG. 2D. The voltage across the capacitor 18 is applied to the positive input terminal of the second comparator circuit 10, but when the voltage across the capacitor 18 exceeds the reference voltage applied to the negative input terminal, the voltage across the capacitor 18 is applied to the positive input terminal of the second comparison circuit 10.
An "H" signal is generated at the output terminal of the RS flip-flop circuit 8 and is applied to the reset input terminal R of the R-S flip-flop circuit 8 as a reset signal. Therefore, the inverting output terminal of the R-S flip-flop circuit 8 is
The signal becomes "H", the base voltage of the switching transistor 14 becomes "L", the switching transistor 14 is turned off, and muting is canceled. At the same time, the shorting transistor 16 is turned on, the capacitor 18 is discharged, and the signal applied to the positive input terminal of the second comparison circuit 10 becomes "L".
Therefore, the input signal to the reset input terminal R of the R-S flip-flop circuit 8 also becomes "L".

Therefore, muting of _T1 is performed for a certain period of time after the playback button is operated, and noise accompanying switching can be prevented from occurring.

Next, a case will be described in which a tape recorder in a playback state is changed to a recording state. Now, at time B, if the stop button is pressed to stop the reproducing state, the motor switch 7 is opened and the trigger switch 6 is closed for a short time. The drive motor 3 rotates due to inertia for a predetermined period of time, and shifts the mechanical mechanism 5 from the regeneration state to the stop state.

On the other hand, when the trigger switch 6 is closed for a short time, the control transistor 20 is turned on, and muting is performed by the same circuit operation as when the playback button is operated. Therefore, the noise generated when the stop button is operated is also effectively eliminated by the mutating.

Subsequently, when the recording button is pressed at time C, the trigger switch 6 and motor switch 7 are closed, the drive motor 3 rotates, and the mechanical mechanism 5 shifts to the recording state. At this time, the various recording/reproducing changeover switches are driven by the mechanical mechanism 5 and are switched from the playback state to the recording state, and at the same time the detection switch 19 is also switched from the playback position indicated by the solid line to the recording position indicated by the broken line. Muting is started immediately by closing the trigger switch 6. However, since the switching of the recording/reproducing switch is accompanied by the movement of the mechanical mechanism 5, a time delay occurs, and it takes time for the circuit switched by the previous recording/reproducing switch to become stable.

Therefore, when operating an operation button that does not involve switching the recording/playback switch, muting is performed for a sufficient period of time for the mechanical mechanism 5 to switch, so that the signal generation time is as short as possible, and the operation button does not involve switching the recording/playback switch. When operating the operation button, a time-variable muting circuit is required to obtain a sufficient muting time by taking into account the time required for the switched circuit to stabilize.

When changing from the playback state to the stop state and then to the recording state, the trigger switch 6 is closed for a short time by pressing the record button at time C, and the control transistor 2 is closed.
0 is turned on for a short time, an "H" signal is applied from the output terminal of the first comparator circuit 9 to the set input terminal S of the R-S flip-flop circuit 8, and the inverted output terminal becomes "L", so that the switching transistor 14 is turned on, and mutating is performed immediately. At the same time, the shorting transistor 16 is turned off and charging of the capacitor 18 is started. At time D, when the movable contact piece of the shooting type detection switch 19 moves from the short-circuited state between the terminals 19a and 19b to the short-circuited state between the terminals 19b and 19c, the terminal 19a is grounded in the middle of the movement. Ru. Therefore, at time D, the charge accumulated in the capacitor 18 is discharged to the ground via the detection switch 19, the voltage across the capacitor 18 becomes zero, and then when the state of switching to the ground is released, the charge is discharged to the ground again. Charging of the capacitor 18 is started. When the voltage across the capacitor 18 reaches a predetermined value, an "H" signal is generated at the output terminal of the second comparison circuit 10, which is applied to the reset input terminal R of the R-S flip-flop circuit 8, and is applied to the inverting output terminal. becomes “H”, switching transistor 14 is turned off, and shorting transistor 1 is turned off.
6 is turned on and muting is canceled.

As is clear from FIG. 2D, when the switching of the recording/reproduction switch is involved, the muting time is the time _T2 from the closing of the trigger switch 6 to the switching of the detection switch 19, and the time T2 from the switching of the detection switch 19 to the switching of the detection switch 19. _The sum (T ₁
+T ₂ ). Therefore, a sufficient amount of muting time is achieved, including time for the switched circuit to stabilize.

Particularly, in a tape recorder in which a mechanical mechanism is driven by a drive motor of this kind and a recording/playback switch is switched by the mechanical mechanism, the time from pressing the operation button to the end of switching is variable, and the muting circuit according to the present invention By making the time from the end of switching to the end of muting constant, the above-mentioned variations can be sufficiently absorbed.

As described above, the mutating device according to the present invention can effectively perform mutating even when the period from the start of operation of the operating section to the end of the operation according to the operation of the operating section is significantly different. In particular, it is suitable for use in a switching device in which a mechanical mechanism is driven by the operation of an operating section, and the mechanical mechanism may or may not switch a changeover switch.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a characteristic diagram showing waveforms of each part thereof. Explanation of main figure numbers, 8...R-S flip-flop circuit, 9, 10... Comparison circuit, 14... Switching transistor, 18... Capacitor, 19
...Detection switch.

Claims (1)

[Claims] 1. A muting device for a switching device configured to drive a mechanical mechanism by a motor that starts rotating when an operation unit is operated, and to switch a recording/playback circuit changeover switch by the mechanical mechanism, which operates as described above. a first means for generating a control signal in response to the start of operation of the part; a second means for performing muting in response to the control signal from the first means; and an operation in response to the control signal from the first means. a third means for starting and measuring a predetermined time; a fourth means for detecting that the third means has measured the predetermined time and stopping the first means from generating the control signal; fifth means for detecting that the switch has been switched;
and a sixth means for resetting the third means in response to the output signal of the fifth means, and when the output signal of the fifth means is generated, the sixth means resets the third means before the measured time of the third means reaches a predetermined time. A mutating device characterized in that the third means is reset by means of a means, and measurement is started again to delay reaching a predetermined time to extend the muting time.