Abstract: A method and apparatus capable of generating and executing large numbers of functional tests for complex digital electronic systems at low cost are presented. The apparatus includes a test generator which uses a decision tree representation of a verification space, derived from a functional specification of the digital electronic system, to generate functional tests. A decision tree representation of a verification space includes an initial goal node, a leaf goal node, and at least one intermediate goal node interconnected by a plurality of directed decision arcs formed between the initial goal node and the leaf goal node. Goal plans assigned to goal nodes include operations which generate functional tests. Functional tests are generated by recursively “walking” the decision tree, the choices of which goal node to visit next being made at random and according to decision weights assigned to each goal node.

Abstract: A method and apparatus capable of generating and executing large numbers of functional tests for complex digital electronic systems at low cost are presented. The apparatus includes a test generator which uses a decision tree representation of a verification space, derived from a functional specification of the digital electronic system, to generate functional tests. A decision tree representation of a verification space includes an initial goal node, a leaf goal node, and at least one intermediate goal node interconnected by a plurality of directed decision arcs formed between the initial goal node and the leaf goal node. Goal plans assigned to goal nodes include operations which generate functional tests. Functional tests are generated by recursively "walking" the decision tree, the choices of which goal node to visit next being made at random and according to decision weights assigned to each goal node.

Abstract: An improved, jam-resistant, relatively low cost pencil mechanism is provided which includes an annular resilient member disposed about the nose bushing of the mechanism for securely locking the bushing and lead guide connected thereto in place within the pencil barrel, while at the same time allowing the pencil tip and lead guide to be threadably interconnected without creating open thread discontinuities along the length of the lead path. The resilient member serves to take up any dimensional irregularities in the pencil mechanism components and allow full threaded interlocking of the pencil tip and lead guide so that no exposed threads are present along the lead path, which can cause jamming of the mechanism if the pencil lead becomes broken within the guide. In preferred forms, the resilient member is of annular, tapered configuration permitting telescopic positioning thereof within the pencil barrel without disruption or axial roll-up of the member.

Abstract: A pneumatic speed control device for an automotive vehicle that derives its power from a vehicle engine manifold vacuum and is an adaptive control which maintains a constant vehicle speed by means of changing the throttle position due to a deviation from vehicle speed which has been selected by the driver. This device includes a differential control valve for controlling a vacuum signal leading to a bellows actuating the throttle linkage of the vehicle and a speed sensing device including a control valve for a vacuum signal proportional to the vehicle speed and communicating with one side of a diaphragm in the differential control valve; the opposite side of the diaphragm communicating with an accumulator of a fixed volume which receives the vacuum signal from the speed sensing device and is isolated therefrom once the desired cruising speed is reached.

Abstract: A constant speed drive system which is automatically controlled according to the load of the pump, fan, etc. driven by the system. Control of the system is achieved by means of a pump or compressor and a diaphragm-actuated spool valve, wherein a reference point or pressure in a spool valve is matched with a pressure, proportional to the speed of the load or output shaft, acting on a diaphragm in the spool valve. The spool valve, in turn, modulates the pressure to a clutch actuator for a clutch located between a constant speed motor and a shaft driving the requisite load.