Abstract: A portable electronic device includes a player, a speaker, a control circuit, a switch circuit, and a current limiter. The player is for outputting analog audio signals. The speaker is for transforming the analog audio signals into sound. The control circuit is for generating a first control signal when ambient light intensity is lower than a predetermined value. The switch circuit is for turning on and transmitting the analog audio signals to the speaker when receiving the first control signal. The current limiter is for transmitting the analog audio signals to the speaker when the switch circuit turns off, and for limiting a current flowing through the speaker.

Abstract: A scanning circuit includes n rows L1˜Ln, 2n columns P1-1˜P1-n and P2-1˜P2-n, and the n rows L1˜Ln and the n columns P1-1˜P1-n cooperatively form a switch matrix comprising n*n switches S1-1˜Sn-n, with ends of the switches in the same row electrically connected to one of n I/O ports K1˜Kn, respectively, the ends of the switches in the same column are electrically connected to ground via one resistor R1-1˜R1-n, respectively, each of resistors R2-1˜R2-n is electronically connected in one column of the columns P2-1˜P2-n, and connected between one of the I/O ports K1˜Kn and ground via one of the resistors R1-1˜R1-n, respectively. A keyboard and a scanning method are also provided.

Abstract: A telephone line monitoring device is connected to a telephone line and adjacent to a telephone device using the telephone line. The telephone line monitoring device includes a rectifying circuit for generating a corresponding direct current voltage according to an effective voltage of the telephone line; a first controller for generating a first control signal when the direct current voltage is lower than a predetermined voltage; a second controller for detecting an operating state of the telephone device and generating a second control signal when the telephone device is operated; a load booster for pulling down the effective voltage of the telephone line when enabled; and a first switch circuit for disabling the load booster whenever receiving the second control signal, and enabling the load booster when receiving the first control signal while not receiving the second control signal. A monitoring method and a telephone device are also provided.

Abstract: A scanning circuit includes n rows L1˜Ln, 2n columns P1-1˜P1-n and P2-1˜P2-n, and the n rows L1˜Ln and the n columns P1-1˜P1-n cooperatively form a switch matrix comprising n*n switches S1-1˜Sn-n, with ends of the switches in the same row electrically connected to one of n I/O ports K1˜Kn, respectively, the ends of the switches in the same column are electrically connected to ground via one resistor R1-1˜R1-n, respectively, each of resistors R2-1˜R2-n is electronically connected in one column of the columns P2-1˜P2-n, and connected between one of the I/O ports K1˜Kn and ground via one of the resistors R1-1˜R1-n, respectively. A keyboard and a scanning method are also provided.

Abstract: An interface circuit and an electronic device are used for expanding an output port of a micro processing unit. The interface circuit includes an input port electrically connected to the output port of the micro processing unit for receiving a control signals, and a plurality of output ports selectively driven to control external circuits by inputting different values of the control signal at the input port.

Abstract: A telephone line monitoring device is connected to a telephone line and adjacent to a telephone device using the telephone line. The telephone line monitoring device includes a rectifying circuit for generating a corresponding direct current voltage according to an effective voltage of the telephone line; a first controller for generating a first control signal when the direct current voltage is lower than a predetermined voltage; a second controller for detecting an operating state of the telephone device and generating a second control signal when the telephone device is operated; a load booster for pulling down the effective voltage of the telephone line when enabled; and a first switch circuit for disabling the load booster whenever receiving the second control signal, and enabling the load booster when receiving the first control signal while not receiving the second control signal. A monitoring method and a telephone device are also provided.

Abstract: An apparatus for adjusting a sound volume includes an ultrasonic transreceiver for transmitting an ultrasonic signal and receiving a reflected ultrasonic signal reflected back from an object, and a volume module for adjusting the sound volume based on a time from transmitting the ultrasonic signal to receiving the reflected ultrasonic signal that has a different frequency from the ultrasonic signal.

Abstract: An interface circuit and an electronic device are used for expanding an output port of a micro processing unit. The interface circuit includes an input port electrically connected to the output port of the micro processing unit for receiving a control signals, and a plurality of output ports selectively driven to control external circuits by inputting different values of the control signal at the input port.

Abstract: A portable electronic device includes a player, a speaker, a control circuit, a switch circuit, and a current limiter. The player is for outputting analog audio signals. The speaker is for transforming the analog audio signals into sound. The control circuit is for generating a first control signal when ambient light intensity is lower than a predetermined value. The switch circuit is for turning on and transmitting the analog audio signals to the speaker when receiving the first control signal. The current limiter is for transmitting the analog audio signals to the speaker when the switch circuit turns off, and for limiting a current flowing through the speaker.

Abstract: An apparatus for protecting a password includes a keypad, a generator, and a processor. The keypad includes numeric keys for inputting a numeral and a display unit for displaying a random digit. The generator is coupled to the display unit for generating the random digit. The processor is configured for receiving the inputted numeral and calculating the password based on the inputted numeral and the random digit.

Abstract: An over-voltage protection circuit is provided herein for protecting a load from an over-voltage condition, and that does not cause a reverse voltage. The over-voltage protection circuit includes a first switch circuit and a second switch circuit. The first switch circuit is for outputting a switch-on signal when the input voltage is lower than or equal to a predetermined value and a switch-off signal when the input voltage is higher than the predetermined value. The second switch circuit for conducting the input voltage to the load when receiving the switch-on signal. An over-voltage protection method is also provided.

Abstract: A battery charging system for receiving an AC voltage and charging a rechargeable battery is provided herein. The battery charging system includes an adapter for rectifying an AC voltage into a first DC voltage; a controller for receiving a battery voltage of a rechargeable battery and outputting a control signal; and a DC switching convertor for converting the first DC voltage into a second DC voltage to recharge the rechargeable battery according to the control signal, wherein the second DC voltage changes according to the battery voltage. A charging method is also provided.