US Patent 7593130 Printing systems

Measurements are taken of a first parameter associated with a first marking engine and of a second parameter associated with a second marking engine. The first and second measurements are compared to predetermined first and second reference values. An engine-to-engine difference is determined by calculating a difference between the first measured parameter and the second measured parameter. The difference values are compared to corresponding predetermined threshold values. Based on the comparison, a system controller selects a mode of operation of the document processing system.