Patent ID: 6191634
Filing Date: 2001-02-20
Classification: G06F

Abstract:
A data communications interface apparatus comprising a signal level conversion circuit interconverting signal levels of a high-power device and a low-power device in order to enable two-way data communication to be performed between said high-power device and said low-power device when said high-power device and said low-power device are connected to each other via a cable;wherein said signal level conversion circuit comprises:a low-to-high power level conversion circuit which receives a signal output from the low-power device and converts a level of the received signal so as to match with an input signal level useable by the high-power device; andwherein said low-to-high power level conversion circuit comprises:a low power source obtaining line to which a power source is supplied from the low-power device; anda first switching device which is switched on when the signal received from said low-power device has a first level, and which is switched off when the signal received from said low-power device has a second level different from the first level;said low-to-high power level conversion circuit controlling a current obtained from said low-power source obtaining line to flow to the high-power device via said first switching device while said first switching device is switched on, thereby applying to said high-power device a signal having a voltage level which is suitable for use by said high-power device; andsaid low-to-high power level conversion circuit opening connection between said first switching device and said high-power device while said first switching device is switched off, and supplying to said high-power device a voltage which is pulled down so as to match with a negative voltage level which is receivable and useable by said high-power device.