JP4711993B2 - Volume control circuit - Google Patents

Description

  The present invention relates to a volume adjustment circuit employed in a receiver, particularly a receiver having a squelch function.

With reference to FIG. 4, an FM receiver employing a conventional volume control circuit will be described.
In this type of FM receiver 100, the received audio signal is input to the variable resistance unit 120 via the squelch switch unit 110. The variable resistance unit 120 controls the resistance value by turning the knob 121, and sets the volume when the received audio signal is amplified by the amplification unit 130 and output from the speaker 140 to a desired volume. It is configured to be able to.
The amplifying unit 130 amplifies the audio signal based on the resistance value set by the variable resistor unit 120 and outputs the audio from the speaker 140.

  The low frequency signal generator 150 generates a beep sound to confirm the presence or absence of such operation when, for example, a specific key is pressed or when each key is pressed, and the amplification unit 130 And the sound is output from the speaker 140. Since the low-frequency signal output from the low-frequency signal generator 150 is not input to the variable resistor 120, but is input to the amplification unit 130 at the subsequent stage of the variable resistor 120, the variable resistor Even if 120 is operated, the volume of the beep sound is not adjusted.

The FM receiver 100 includes the squelch switch unit 110. If the noise level in the received signal is equal to or higher than a set threshold value, the squelch switch unit 110 is placed in the squelch closed state, and the received signal is a variable resistor. If the noise level in the received signal is less than the threshold value, the squelch switch unit 110 is placed in the squelch open state, and the received signal is input to the variable resistor unit 120. It is configured to be.
Japanese Laid-Open Patent Publication No. 5-48475 (Patent Document 1) discloses a volume adjustment technique for outputting sound from a speaker for a certain period of time when volume adjustment is performed even in squelch close.

Japanese Patent Laid-Open No. 5-48475

When the volume is adjusted by the conventional FM receiver 100 as described above, the knob 121 of the variable resistor 120 is turned to adjust the volume to a desired level while outputting the received signal from the speaker 140. It has been broken.
However, when the squelch switch unit 110 is in the squelch closed state, no sound is output from the speaker 140, so the volume cannot be confirmed and cannot be adjusted to a desired volume.
In particular, immediately after turning on the power of the FM receiver 100, if the set reception frequency does not match the frequency of the desired broadcast station, radio station, etc., the squelch switch unit 110 will be in the squelch closed state. In some cases, no sound is output from the speaker 140, and the volume cannot be adjusted.
Therefore, at present, in order to set the volume immediately after the power of the FM receiver 100 is turned on, a method of remembering the amount of rotation of the knob 121 of the variable resistance unit 120, or the volume output from the speaker 140 is maximum. The variable resistor 120 is set so that the signal is received by changing the reception frequency so as to be in the squelch open state, and then the volume is adjusted by the variable resistor 120 while outputting sound from the speaker 140. The way to be executed.
However, in the former method, it is complicated to remember the amount of rotation of the knob, and in the latter method, there is a problem that it may take time to find a reception frequency that is in a squelch open state. .

  Further, the technique disclosed in Japanese Patent Application Laid-Open No. 5-48475 has a problem that the volume of the sound serving as a reference for sound adjustment varies depending on the situation and is not constant, and it is difficult to adjust the volume.

  Therefore, the present invention has been made for the purpose of providing a circuit configuration capable of appropriate volume adjustment in a receiver.

In the volume control circuit of claim 1 according to the present invention,
Control that determines that the squelch is open if the noise level of the noise component in the received signal is less than a predetermined threshold, and determines that the squelch is closed if the noise level of the noise component in the received signal is greater than or equal to the threshold. A squelch switch that passes the received signal when the control unit determines that the squelch is closed, and the control unit determines that the squelch is closed. A volume adjustment circuit for a receiver, comprising: a volume adjustment unit that can output a reception signal that has passed through the squelch switch unit at a desired volume set by operating the volume setting unit;
A power detection unit for detecting that the receiver is turned on;
A low-frequency signal generation unit that generates a predetermined low-frequency signal,
Furthermore, the control unit
When the power detection unit detects that the receiver is turned on, during the first set time,
Regardless of the noise level of the noise component in the received signal,
The squelch switch unit is in a squelch closed state, and the low frequency signal generated by the low frequency signal generation unit is input to the volume adjustment unit.
In claim 2,
The volume adjuster is
An operation detection unit for detecting the presence or absence of an operation for changing the volume in the volume setting unit;
The controller is
When the operation detecting unit detects that there is an operation for changing the volume in the volume setting unit during the second set time before the end of the first set time, Regardless of the noise level of the noise component,
The squelch switch unit is placed in a squelch closed state, and the low-frequency signal generated by the low-frequency signal generation unit is continued for a predetermined extension time after the first set time is ended. It was configured to be input.
In claim 3,
In the volume setting section,
A power switch for on / off control of the power supply of the receiver is integrally provided.
In claim 4,
The controller is
The length of the first set time can be set to a desired length.

In the invention of claim 1,
A power detection unit for detecting that the power of the receiver is turned on, and a low frequency signal generation unit for generating a predetermined low frequency signal,
Further, when the power source detection unit detects that the power source of the receiver is turned on, the squelch switch unit is squelched for a first set time without being related to the noise level of the noise component in the received signal. Since it is in a closed state and has a control unit that inputs the low frequency signal generated by the low frequency signal generation unit to the volume adjustment unit, even if there is no reception signal immediately after power on, the reception signal Even if the level is not constant, it is possible to adjust the volume appropriately while listening to the generated low frequency signal.
In the invention of claim 2,
The volume adjustment unit includes an operation detection unit that detects the presence or absence of an operation for changing the volume in the volume setting unit,
The controller is
When the operation detecting unit detects that there is an operation for changing the volume in the volume setting unit during the second set time before the end of the first set time, Regardless of the noise level of the noise component, the squelch switch unit is placed in the squelch closed state, and the low frequency signal generating unit generates a low frequency signal for a predetermined extension time after the first set time is over. Since the configuration is such that the frequency signal is continuously input to the volume adjustment unit, if the volume adjustment operation is continued, the generated low level signal continues even after the first set time has elapsed. You can adjust the volume appropriately while listening to the frequency signal.
In the invention of claim 3,
In the volume setting section,
Since the power switch for controlling on / off of the power supply of the receiver is integrally provided, space efficiency is improved, and power on / off operation and volume adjustment can be performed efficiently.
In the invention of claim 4,
The controller is
Since the length of the first set time can be set to a desired length, the length of the first set time can be set to a desired length according to the time that the user of the receiver is expected to adjust the volume. Can be set.

  Hereinafter, a sound volume adjusting circuit according to the present invention will be described in detail with reference to the drawings showing embodiments thereof.

As shown in FIG. 1, the volume adjustment circuit according to the present invention is employed in a receiver 1 such as an FM receiver, for example, and a reception signal received by a reception unit 2 passes through a squelch switch unit 3. Are input to the variable resistor 41 of the variable resistor section 4.
The opening / closing control of the squelch switch unit 3 is performed by a control unit 5 including a CPU.

  The control unit 5 determines whether to squelch open or squelch close from a noise component in the received signal. The control unit 5 outputs an open signal to the squelch switch unit 3 in order to place the squelch switch unit 3 in a squelch closed state if the noise level of the noise component in the received signal is equal to or higher than a predetermined threshold value. If the noise level of the noise component in the received signal is less than the threshold value, a closed signal is output to the squelch switch unit in order to set the squelch open state. The threshold value can be changed.

  When the open signal is input from the control unit 5, the squelch switch unit 3 enters a squelch closed state, blocks the received signal without passing it, and does not input it to the amplifier unit 6. When the closed signal is input from the control unit 5, the squelch open state is established, and the received signal is passed through and input to the amplification unit 6.

The variable resistance unit 4 can control a resistance value by turning a knob, and includes a variable resistor 41 having a knob 411 mounted on a rotating shaft, for example. The variable resistance unit 4 is for setting the volume when the reception signal is output from the speaker 7 to a desired volume.
In this embodiment, a variable resistor 41B with an on / off switch as shown in FIG. Such a variable resistor 41B with an on / off switch rotates the knob 411B so that a mark 412B such as an arrow displayed on the surface of the knob 411B coincides with an “OFF” position 413B displayed on the panel. The power switch 92 is turned off to turn off the power, and the power switch 92 is turned on by rotating the knob 411B so that the mark 412B coincides with the area of the “ON” position 414B displayed on the panel. So that the power can be turned on.

  The operation detection unit 42 detects whether or not the resistance value of the variable resistor unit 4 has changed during a predetermined second set time. When the operation detection unit 42 detects that there is a change, the operation signal is sent to the detection signal. Output to the control unit 5.

  The amplifying unit 6 is configured to amplify the received signal to a volume based on the resistance value set by the variable resistor unit 4 and output the amplified signal from the speaker 7.

The low frequency signal generation unit 8 generates a low frequency signal such as a beep sound or an alarm sound, and inputs the low frequency signal to the adjustment low frequency signal switch 81 and the operation confirmation low frequency signal switch 82.
The adjustment low-frequency signal switch 81 is controlled to be turned on and off by the control unit 5, and the low-frequency signal such as a beep sound or an alarm sound generated by the low-frequency signal generation unit 8 is variable. It is configured to control whether or not to output to the resistance unit 4, and is controlled for use in volume adjustment after the power is turned on.
The operation confirmation low frequency signal switch 82 is controlled to be turned on and off by the control unit 5, and the low frequency signal such as a beep sound or an alarm sound generated by the low frequency signal generation unit 8 It is configured to control whether to output to the amplifying unit 6 or not. For example, it can be used to confirm the presence or absence of an operation when a specific key is pressed or when each key is pressed.

  When the power supply detection unit 9 detects that the power supply device 91 of the receiver is turned on, the power supply detection unit 9 outputs a power-on detection result to the control unit 5.

Next, the operation of the volume adjustment circuit according to the present invention will be described with reference to FIG.
When the power supply of the receiver is turned on, the power supply detection unit 9 detects that the power supply is turned on and outputs a detection result to the control unit 5 (see S1). Then, the said control part 5 starts the measurement of the elapsed time after a power supply was turned on during 1st setting time (refer S2).
Further, when the detection result is input from the power supply detection unit 9, the control unit 5 supplies the squelch switch unit 3 during the first set time regardless of the noise level of the noise component in the received signal. Control is performed to output an open signal to a squelch closed state (see S3). The length of the first set time can be set to a desired length. For example, any one of 2 seconds, 5 seconds, and 10 seconds may be selected and set.
The first set time can be set according to the time predicted by the user of the receiver to adjust the volume.
In this way, the squelch is closed during the first set time, and the received signal is cut off even when the received signal is received.

  Further, when the detection result is input from the power source detection unit 9, the control unit 5 controls the low frequency signal generation unit 8 to generate a low frequency signal such as a beep sound signal and the adjustment low level signal. The frequency signal switch 81 is controlled to input the low frequency signal to the variable resistor unit 4 (see S4). At this time, since the squelch is closed, the received signal is blocked even when the received signal is received, and only the low-frequency signal is output from the speaker, so that appropriate volume adjustment is possible.

  The low-frequency signal input to the variable resistor unit 4 is output from the speaker 7 at a volume based on a resistance value controlled by turning the knob of the variable resistor unit 4. By adjusting the rotation angle, the low-frequency signal output from the speaker 7 can be adjusted to a desired volume.

The control unit 5 uses a second set time (for example, 0.5 seconds, 1 second, 2 seconds, etc.) before the end of the first set time as a monitoring time, during the second set time. The operation detection unit 42 monitors whether or not the operation of the knob is detected. (See S5 and S6).
For example, if the first set time is 10 seconds and the second set time is 1 second, 9 seconds after the power is turned on (= (first set time: 10 seconds) − (second set From time: 1 second), the presence or absence of the knob operation is monitored for 1 second, which is the second set time.
Then, when a detection signal is detected during the second set time, it is determined that the volume adjustment work is continued, and the control unit 5 receives the signal after the first set time is over. Regardless of the noise level of the noise component in the signal, the squelch closed state is continuously maintained for a predetermined extended time, the adjustment low-frequency signal switch 81 is turned on, and the low-frequency signal generating unit 8 changes the variable resistance. The low frequency signal is input to the unit 4 (see S7).
By doing so, the low frequency signal is output from the speaker 7 even after the first set time has elapsed, so that the volume adjustment operation can be continued.
When the detection signal indicating that the knob has been operated is detected again during the extension time, the control unit 5 sets the noise level of the noise component in the reception signal after the extension time. Without being involved, the squelch closed state is continuously maintained for the extended time, the adjustment low frequency signal switch 81 is turned on, and the low frequency signal is input from the low frequency signal generator 8 to the variable resistor 4. This is repeated (see S7 and S8), and the low-frequency signal is continuously output from the speaker 7 until the detection signal indicating that the knob has been operated during the previous extended time is not detected.

If the detection signal is not input during the extension time, it is determined that the volume adjustment work by the low frequency signal is not continued, and the control unit 5 determines the adjustment low frequency signal switch 81 or the low frequency signal. The generator 8 is controlled to stop the output of the low frequency signal (see S8, S9, and S10). By doing so, the output of the low frequency signal from the speaker 7 is stopped.
Thus, after stopping the output of the low frequency signal, the control unit 5 squelch closes the squelch switch unit 3 if the noise level of the noise component in the received signal is equal to or higher than a predetermined threshold value. If the noise level is less than a predetermined threshold value, the squelch switch unit 3 is controlled to a squelch open state.

In this way, during the first set time immediately after the receiver 1 is turned on, a low frequency signal such as a beep sound is output from the speaker 7, so that the knob is rotated while listening to the low frequency signal. By doing so, it can be adjusted to a desired volume.
Further, if it is detected that the knob is operated for volume adjustment during the second set time before the end of the first set time, the noise level of the noise component in the received signal is not affected. Further, since the low frequency signal such as a beep sound is output from the speaker 7 for a predetermined extension time after the first set time is finished, the volume adjustment operation can be continued.
Furthermore, even after the first set time has expired, if it is detected that a knob has been operated for volume adjustment during the second set time before the extended time has expired, Since the low frequency signal such as a beep sound is further output from the speaker 7 for a predetermined extension time after the extension time is over, regardless of the noise level of the noise component in the signal, the volume adjustment work is performed. Can continue.
If the knob is not operated to adjust the volume during the extension time, it is determined that the volume adjustment operation has been completed, and the output of the low frequency signal is stopped, so that the normal reception state can be entered.

Note that the second set time as the monitoring time for monitoring the presence or absence of the knob operation and the extension time may be the same length, but the extension time is equal to or longer than the second set time (monitoring time). If so, the time may be different.
In the above embodiment, since the variable resistor 41 with the on / off switch integrated with the power switch 92 is used for the variable resistor section 4, the amount of rotation of the knob that outputs an appropriate sound volume is memorized. You can adjust the volume every time the power is turned on.
Note that the present invention is not limited to such a variable resistor with an on / off switch, but includes a configuration in which the power switch and the variable resistor section are separated from each other. Yes.
Further, the adjustment low-frequency signal switch 81 and the operation confirmation low-frequency signal switch 82 may be integrated without being separated, or may be included in the low-frequency signal generator 8.
In addition, for users who do not use the function of the present invention, it is possible to set the function to be invalid and use it like a conventional receiver.

It is the block diagram which showed the structure of embodiment of the volume control circuit concerning this invention. It is a flowchart explaining operation | movement of the said volume adjustment circuit. It is a figure which shows an example of the knob used for the said volume control circuit. It is a block diagram of the FM receiver of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Receiver 2 Reception part 3 Squelch switch part 4 Variable resistance part 41 Variable resistor 42 Operation detection part 411 Knob 5 Control part 6 Amplification part 7 Speaker 8 Low frequency signal generation part 81 Low frequency signal switch 82 for adjustment Low for operation confirmation Frequency signal switch 9 Power supply detection unit 91 Power supply device 92 Power supply switch

Claims (4)

Control that determines that the squelch is open if the noise level of the noise component in the received signal is less than a predetermined threshold, and determines that the squelch is closed if the noise level of the noise component in the received signal is greater than or equal to the threshold. And a squelch switch unit that closes a squelch and cuts off a reception signal, and when the control unit determines that the squelch is open, a squelch switch unit that opens the squelch and passes a reception signal, A volume adjustment circuit for a receiver, comprising: a volume adjustment unit that can output a reception signal that has passed through the squelch switch unit at a desired volume set by operating the volume setting unit;
A power detection unit for detecting that the receiver is turned on;
A low-frequency signal generation unit that generates a predetermined low-frequency signal,
Furthermore, the control unit
When the power detection unit detects that the receiver is turned on, during the first set time,
Regardless of the noise level of the noise component in the received signal,
A volume adjustment circuit configured to place a squelch switch unit in a squelch closed state and to input a low frequency signal generated by the low frequency signal generation unit to the volume adjustment unit. The volume adjuster is
An operation detection unit for detecting the presence or absence of an operation for changing the volume in the volume setting unit;
The controller is
When the operation detecting unit detects that there is an operation for changing the volume in the volume setting unit during the second set time before the end of the first set time, Regardless of the noise level of the noise component,
The squelch switch unit is placed in a squelch closed state, and the low-frequency signal generated by the low-frequency signal generation unit is continued for a predetermined extension time after the first set time is ended. The sound volume adjustment circuit according to claim 1, wherein the sound volume adjustment circuit is input to the sound volume. In the volume setting section,
The volume control circuit according to claim 1, wherein a power switch for controlling on / off of a power supply of the receiver is integrally provided. The controller is
4. The volume adjustment circuit according to claim 1, wherein the length of the first setting time can be set to a desired length. 5.

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