Abstract: An input device capable of being connected to a computing device includes a housing having transducer electronics capable of manipulating an electrical signal to indicate movement of a portion of a user. At least one but fewer than four conductors are connected to the transducer electronics, and are each capable of carrying an electrical signal related to the input device. Each of the conductors is coupled to a connector that is capable of being coupled to the computer.

Abstract: A computer input device uses a standard mouse design and includes at least one thumb wheel or roller to provide three-dimensional cursor positioning. Left and right rollers, for use by left- and right-handed users, protrude from left and right sides of a standard mouse. The left and right rollers are axially mounted on left and right drive shafts that extend axially through left and right encoder wheels, respectively. Each encoder wheel forms part of a transducer for producing signals indicating movement or rotation of the wheel. These signals can be used for calculating cursor movement or for various other purposes in computer software applications. Alternatively, the rollers are coupled to switches or a single roller protrudes from the top of the mouse.

Abstract: A circuit using a single transistor to detect the interface type to Which a combination pointing device is connected. The pointing device may be connected to a PS/2 interface, which generates a voltage greater than or equal to 0 volts, or a serial interface which generates a negative voltage. The transistor is activated when connected to the serial interface, and is inactive when connected to the PS/2 interface. The output of the transistor is sensed by a microcontroller within the pointing device. The microcontroller generates data for transmission to the PS/2 interface if the transistor is not active, and generates data for transmission to the serial interface if the transistor is active. An I/O pin in the microcontroller is used to sense the interface type and can also be used as an output in which the microcontroller generates control signals for use by the pointing device. This multitasking operation reduces the required pin count of the microcontroller, thus reducing cost.

Abstract: A method of detecting quadrature signals in a computer input device allows a microprocessor in the input device to perform comparator functions, thus eliminating the need for external comparator circuitry. At least one light-emitting element in the input device emits light pulses, and these light pulses are selectively received by a light-detecting element. A notched encoder wheel separates the light-emitting element from the light-detecting element, allowing various amounts of light to be received by the light-detecting element depending on whether a notch separates the two elements. The microprocessor loads a sample of the output from the light-detecting element: a first sample taken at a selected time value and a second sample taken at twice the selected time value. The second sample is used for quadrature calculations used in determining cursor movement on a video display device. The first sample is retrieved by the microprocessor and determined if it is a digital "1" signal.

Abstract: A computer input device uses a standard mouse design and includes at least one thumb wheel or roller to provide three-dimensional cursor positioning. Left and right rollers, for use by left- and right-handed users, protrude from left and right sides of a standard mouse. The left and right rollers are axially mounted on left and right drive shafts that extend axially through left and right encoder wheels, respectively. Each encoder wheel forms part of a transducer for producing signals indicating movement or rotation of the wheel. These signals can be used for calculating cursor movement or for various other purposes in computer software applications. Alternatively, the rollers are coupled to switches or a single roller protrudes from the top of the mouse.

Abstract: A coupling circuit for a multimeter adapted to perform multiple measurements includes a thermistor and constant current sources in series between an instrument input terminal and an instrument circuit adapted to source current for ohms measurements. Varistors shunt the constant current sources and are thermally coupled to the thermistor. An initial inrush of current is controlled by the constant current sources and when the voltage across a constant current source reaches the knee voltage of the paralleled varistor, the varistor shunts the constant current source and provides heat to the thermistor for insuring the latter will transition to its high resistance state. The thermistor then drops a substantial part of the input voltage, effectively disconnecting the low impedance ohms circuit from the input terminals and protecting the constant current source circuitry and varistors from extended application of high voltage.

Abstract: A protective circuit for the input of a multimeter is provided with series connected thermistors partially shunted by a varistor whereby overload voltage is distributed between the thermistors enabling protection at higher voltage levels. Shunt connected varistors protect primarily against transient overloads and are thermally coupled to the aforementioned thermistors to bring the thermistors more rapidly to their high resistance condition such that damage to the varistors is avoided and continued protection is provided.

Abstract: A thermistor device includes plural thermistor elements in series, one or more of which is shunted with a varistor so that if such thermistor heats up and drops excessive voltage, the current therethrough is diverted to the varistor until other thermistors in series also heat to a high resistance state. The thermistor and varistor elements are thermally joined so that the various thermistor elements are rapidly brought up to temperature and prevent prolonged voltage drop across a protective varistor.

Abstract: A digital multimeter having automatic function selection capability includes a signal type detector and an analog-to-digital converter formed as an application specific integrated circuit. The signal type detector has a comparator circuit that compares the analog input signal to be measured with predetermined thresholds and stores the resulting values, which are related to the type of analog input signal, in a memory that is also a part of the signal type detector. A controller executes an automatic function selection program that causes the controller to read the stored values and generate a corresponding function code, which causes an analog-to-digital converter to be configured to perform an appropriate conversion function on the analog input signal. When a change in the type of analog input signal is sensed, the controller aborts the present measurement cycle and proceeds with a next measurement cycle in which the changed analog input signal is measured.

Abstract: The capacitance of an unknown capacitor is measured with multimeter instrumentation employing a dual slope analog-to-digital converter. The initial voltage across the capacitor is measured and the capacitor is cyclically charged until the capacitor reaches a predetermined proportion of possible charge. The final voltage is measured. The voltage across the charging resistance is integrated over successive charging cycles to provide a value proportional to the charge delivered to the capacitor and this value is divided by the difference between the initial and final voltages.