Method and circuitry for implementing VCOs with improved frequency band switching use differentially-coupled varactors to implement the different frequency bands. A working gas undergoes four thermodynamic processes that comprise a Brayton cycle. The carrier may subsequently be unlatched to permit removal of the portable display device for use for display purposes, and relatched for subsequent transportation. In the process, steam released by the iron penetrates the garments and enters the enclosure through the ironing board.