Abstract: A plurality of electrical load switches of the type operable to at least two operating conditions by the actuation of an operating member are connected in respective motor vehicle load circuits and are mounted in a switching unit having an actuating mechanism for actuating the switch operating members that is selectively locatable in each of a plurality of switch operating positions in each of which it is in register with an operating member. The switching unit is controlled by a microprocessor that effects the locating of the actuating mechanism in the switch operating position in which it may actuate the operating member of a load switch selected to be operated and the operating of the actuating mechanism when so located in response to function select electrical signals that indicate the load switches selected for operation.

Abstract: A plurality of individual electrical load switches each having an operating tab are so mounted and oriented that the operating tabs extend toward a central axis to define a circle substantially normal to the central axis and operate substantially in the direction of the central axis. An operating arm having ends thereof arranged to be brought into register with each operating tab at mutually exclusive angular positions is normally tilt mounted in a first direction upon a rotor that may be positioned in selected ones of a plurality of angular positions by a step motor. Upon one end of the arm being brought into register with a switch operating tab, the arm is tilted in the opposite direction to effect the operation of the operating tab with which the one end thereof is in register to place the corresponding individual electrical load switch in a selected circuit condition.

Abstract: A read only memory is pre-programmed to produce an output binary signal representation of a predetermined ignition spark timing angle based upon the instantaneous value of both of two selected engine operating parameters at each of a plurality of respective selected points within the range of values in response to respective input address signals. Over the range of values of the two selected engine operating parameters, therefore, the read only memory generates a three-dimensional surface of ignition spark timing angles. The binary signal representations of the ignition spark timing angles retrieved from the read only memory are varied in accordance with engine manifold vacuum and actual atmospheric pressure to tilt the three-dimensional surface generated by the read only memory about a selected engine parameter value as an axis in an amount substantially inversely proportional to actual atmospheric pressure.