System and method for controlling sound volume

A method for controlling sound volume, comprising the steps of:

• providing a key input unit comprising an “increase” key and a “decrease” key, for receiving a user operation, and generating a controlling signal according to the operation;
• providing an MCU (Microprogrammed Control Unit) to determine whether an elapsed time of the user continuously operating the key input unit is greater than a preset time;
• adjusting volume by a first amount if the elapsed time is less than or equal to the preset time;
• adjusting volume by a second amount if the elapsed time of user pressing the “increase” key is greater than the preset time;
• and
• setting volume as mute if the elapsed time of the user pressing the “decrease” key is greater than the preset time.

A method for controlling sound volume, comprising the steps of:

• providing a key input unit for receiving a user operation, and generating a controlling signal according to the operation;
• providing an MCU (Microprogrammed Control Unit) to determine whether an elapsed time of the user continuously operating the key input unit is greater than a preset time;
• adjusting volume by a first amount if the elapsed time is less than or equal to the preset time;
• and
• adjusting volume by a second amount if the elapsed time is greater than the preset time.

A method for controlling sound volume, comprising the steps of:

• receiving a volume-adjusting signal from a user-controllable key input unit;
• measuring elapsing time of existence of said signal due to user's operation to said key input unit;
• and
• adjusting said sound volume by means of at least two selectable adjustment speeds, a larger one of said at least two adjustment speeds being in use in case of said measured elapsing time being larger than a predetermined value, and a smaller one of said at least two adjustment speeds being in use in case of said measured elapsing time being smaller than said predetermined value.