Patent ID: 6233285
Filing Date: 2001-05-15
Classification: H04L

Abstract:
An intrinsically safe drive circuit for driving digital signals across a cable between a fist location and a second location comprising:a first terminal for connection to a first digital signal;a second terminal connected to a first end of said cable with a second end of said cable connected to a device at said second location;pull up means connected to said second terminal;first transistor switching means connected to said second terminal, said switching means responsive to said first digital signal, said switching means pulling said second terminal to a first logic level when said switching means is turned on and said pull up means pulling said second terminal to a second logic level when said switching means is turned off;charge storage means connected to said pull up means, said charge storage means incrementally charging each time said pull up means pulls said second terminal to said second logic level; andcontrol means for limiting said first digital signal to a first portion of a first period of time such that said charge storage means incrementally discharges during said first portion of said first period of time and does not incrementally discharge during a second portion of said first period of time allowing said charge storage means to recharge during said second portion of said first period of time.