For this industrial electronics project I have I have to interface a computers digital outputs from a microcontroller to an I/O card using potter and brumfield modules. The problem I am encoutering is that I can't change the digital output voltage to a negative properly im running it into 741 set as an inverter, the digital high works as planned but when it is supposed to be a low voltage it still sends out the -5 voltage to the I/O card turning it on, any ideas would be appreciated.