disclosed is a computer data interface for connecting a hand - held computer and a desktop computer . the computer data interface includes a cable having connectors at each end . a voltage conversion circuit is mounted adjacent to one of the connectors . the voltage conversion circuit receives data signals from the hand - held computer and transmits the signals to the desktop computer at voltage levels compatible with the desktop computer , similarly , the voltage conversion circuit receives signals from the desktop computer and transmits the signals to the hand - held computer at voltage levels compatible with the hand - held computer .