Audio signal amplifier device for use in e.g. mobile telephone, has user interface with pressure-sensitive pushbutton for receiving user commands, and output device comprising LEDS for output of optical signals

摘要

The amplifier device (3) comprises a battery for providing a supply voltage, and an input for receiving input audio signals. An amplifier circuit amplifies the input audio signals to be provided to a speaker. A user interface has pressure-sensitive pushbuttons (150) for receiving the user commands, and output device comprising LEDS (41-43) for output of optical signals showing states of amplifier apparatus. A control circuit is provided to detect commands based on alteration of capacitance of a capacitor of pressure-sensitive pushbutton by pressure change on pushbutton.