A method for assembling a gas turbine engine combustor facilitates reducing costs and time required for assembly. Each CMUT element includes multiple CMUT cells. A bonus is awarded when the outcome includes two or more trigger symbols that have a common first identifying characteristic, wherein at least an aspect of the bonus varies according to the combination of the second identifying characteristics often trigger symbols in the outcome. A layer of contact material is formed on and in contact with the etch stop layer. The image forming apparatus further includes an auxiliary power source configured to drive the first heater. The invention also proposes a corresponding communication method.