A thermal printer is proposed that includes an ink ribbon on which a color ink portion and a non-color ink portion are alternately formed in a conveyance direction, a supply bobbin on which the ink ribbon is wound, a take-up bobbin on which the ink ribbon is to be wound, and a housing that contains the supply bobbin and the take-up bobbin. Additionally, triphenylene containing benzo-fused furan compounds are provided. A typical embodiment is 2,3-dideoxy-2,3-didehydrothymidine 5- phosphoroamidate which can be prepared from phenyl methoxy alaninyl phosphorochloridate and 2,3-dideoxy-2,3-didehydrothymidine. First, hardware and operating-system-component-and-configuration information is extracted in order to conduct a Markov-chain availability analysis of the overall system hardware and operating system to provide a first intermediate result. Parameters of strobe output and current limiting circuit are related and can be set manually or electronically. The display unit receives the display command to accordingly generate a safety indication signal.