Abstract: An aircraft propulsion system comprises first and second thrust producing gas turbine engines. The system comprises a controller configured to determine a required overall propulsion system thrust level, and determine an engine core power level contribution from each aircraft gas turbine engine such that the overall propulsion system produces a minimum overall noise level and meets the required overall propulsion system thrust level. In meeting the minimum overall noise level, at least the first and second gas turbine engines are operated at different engine core power settings.

Abstract: A method of operating a machine, such as a digital printing apparatus, involves installing into the machine a module having a first random number generator associated therewith, and, incidental to installing the module, initiating a second random number generator associated with the machine. The series of random numbers from each generator are checked against each other over time.

Abstract: A method of operating a machine, such as a digital printing apparatus, comprises installing into the machine a module having a first random number generator associated therewith, and, incidental to installing the module, initiating a second random number generator associated with the machine. The series of random numbers from each generator are checked against each other over time.