Abstract: A system and method is provided for preventing a dropout of an LED current. In one embodiment of the present invention, the system includes a voltage source, a first circuit, a second circuit, a controller, and at least one LED. The first circuit receives a reference voltage from the voltage source, receives set-point current data from the controller, and uses the reference voltage and the set-point current data to produce a threshold voltage. The threshold voltage is then provided to the second circuit, where it is converted into an output current, which is drawn through the LED. The second circuit then compares the threshold voltage to an output voltage corresponding to the output current, and provides an output to the controller. The controller then uses the output to determine whether a dropout has occurred. If a dropout has occurred, then second set-point current data is provided to the first circuit.

Abstract: A system and method is provided for preventing a dropout of an LED current. In one embodiment of the present invention, the system includes a voltage source, a first circuit, a second circuit, a controller, and at least one LED. The first circuit receives a reference voltage from the voltage source, receives set-point current data from the controller, and uses the reference voltage and the set-point current data to produce a threshold voltage. The threshold voltage is then provided to the second circuit, where it is converted into an output current, which is drawn through the LED. The second circuit then compares the threshold voltage to an output voltage corresponding to the output current, and provides an output to the controller. The controller then uses the output to determine whether a dropout has occurred. If a dropout has occurred, then second set-point current data is provided to the first circuit.

Abstract: A battery charging circuit sets charging current according to either the capacity of the battery under charge or a constraint of the charging source, depending on the properties of the charging source. The battery charging circuit sets termination current, however, according to the capacity of the battery under charge, regardless of the properties of the charging source. For example, the termination current may be set as a fixed fraction of the recommended C rate of the battery even if the charging current supplied by the charging source is below this C rate. Always setting the termination current in proportion to the battery's capacity permits detection of the current at which charging should terminate even when the charging current is constrained by the charging source and no longer depends on the battery's capacity.

Abstract: A battery charging circuit sets charging current according to either the capacity of the battery under charge or a constraint of the charging source, depending on the properties of the charging source. The battery charging circuit sets termination current, however, according to the capacity of the battery under charge, regardless of the properties of the charging source. For example, the termination current may be set as a fixed fraction of the recommended C rate of the battery even if the charging current supplied by the charging source is below this C rate. Always setting the termination current in proportion to the battery's capacity permits detection of the current at which charging should terminate even when the charging current is constrained by the charging source and no longer depends on the battery's capacity.

Abstract: A portable RF telephone for use in a vehicle may be coupled to an external antenna to overcome the shielding effects of the metallic enclosure of the automobile. While coupled to the external antenna, the portable RF telephone increases the amount of power used to transmit an RF signal. Preferably, the transmit power increases to a maximum level allowed within a defined power classification. Increasing the transmit power overcomes cabling and connector losses associated with using an external antenna and further increases the effective transmitting power without exceeding power levels defined by the telephones power classification.

Abstract: An interface system for connecting various accessory devices to a radiotelephone and arbitrating between conflicting requests for access to the audio channel of the radio telephone by the accessory devices. Included is a controller for controlling operation of the interface system and a switch for connecting the audio channel of the selected accessory to the audio channel of the radiotelephone. A method is also provided for entering user selected operational settings for controlling operation of the interface system and prioritizing access to the radiotelephone.

Abstract: A modular assembly for centrally locating electrical connections of cellular telephone accessories to a cellular telephone near a cellular telephone cradle. An adapter module containing electronics for effectuating the connections is located and mounted beneath the cellular telephone cradle. The adapter contains a plurality of connections for connecting to the cellular telephone accessories.

Abstract: An apparatus for charging a battery has a power supply terminal, a controllable power control switch coupled to said power supply terminal, a charging circuit having a charging terminal for connection to a terminal of the battery, and means for opening and closing the power control switch if a battery is disconnected or connected to the charging terminal, respectively. The means for opening and closing the power control switch may include an analog circuit, a digital circuit, a hybrid analog/digital circuit or a mechanical switch. A method of controlling a power control switch of a battery charging system is disclosed, comprising the steps of generating a reference voltage level, sensing the voltage level at the charging terminal, comparing the voltage level at the charging terminal to the reference voltage, and controlling the power control switch in response to the comparison of the reference voltage level and the voltage level at the charging terminal.