Abstract: Receiving a message including bits corresponding to an identifier, the identifier including a unique address for a aircraft transponder, extracting the unique address from the identifier, comparing the unique address to a set of predetermined addresses, changing selected ones of the identifier bits when the unique address is not one of the set of predetermined addresses, wherein the changing of the identifier bits changes a value of the unique address in the identifier, read-comparing the updated unique address to the set of predetermined addresses and processing the message when the unique address matches one of the set of predetermined addresses.

Abstract: A keyboard system having a plurality of actuable keys is coupled through a central processing unit to an indicia accessing unit for accessing indicia corresponding to said keys. An automatic repeat circuit also interconnects the keyboard system with the central processing unit and includes pressure transducer means responsive to actuating pressure on said keys for producing an amplitude variable signal which causes a signal convertor to produce a corresponding rate variable signal which when fed to the central processing unit causes repetitive accessing of the corresponding indicia at a selectable rate. Feedback from the central processing unit to the repeat circuit determines which key signals are to be operative for repetitive indicia access.