Abstract: A computer system having a power control unit for selection of voltage levels for pluggable cards, such as PCMCIA cards. The computer system includes a primary unit for executing two or more versions of control software (card drivers within the operating system) including a current version of control software. A pluggable PCMCIA card operates with a card voltage and has pins for signalling with a CD signal that the card is plugged into the computer system. The computer includes a power supply for providing at least first and second supply voltages such as 5 V, 3.3 V and x.x V. Power switches select one of the supply voltages as the card voltage. A power control unit controls the power switching unit to select one of the supply voltages. The power control unit includes a voltage select unit operable in response to the current version of the control software for storing a voltage code for specifying the selected one of the supply voltages.

Abstract: Apparatus for converting a dc or analog signal from, for example, a resistance type temperature detector, includes an analog to digital converter which has zero temperature drift. This is achieved by the use of two identical successive approximation digital to analog converters with an external comparator connected to both converters at the same time. By switching, one converter is used to provide zero compensation the other converter being inactive except for utilizing it as the path for the amplifier drift current; then with the switch in its other phase the other converter is activated to convert the analog signal to digital format taking into account the previously computed drift signal.

Abstract: A system and method for measuring the rotational speed of a variable speed drive shaft for a ship or the like with high accuracy over a wide range of speeds. Means associated with the shaft sense the time interval for each turn of the shaft, or fraction thereof. Such time interval is accurately measured and then converted to an r.p.m. value. Steps in the method include counting the number of cycles of an oscillating signal in binary form to measure the time interval for each turn, selecting a most significant portion of bits within the number counted, determining the positional weight of the most significant bit to obtain a scaling factor, and producing a voltage inversely proportional to the value of the selected portion of bits, which voltage is then scaled by the scaling factor.