Interface driver circuit

An interface driver circuit for transmitting signals via a transmission medium, comprising:

• first input means for receiving a first logic signal of a first polarity;
• second means for receiving a second logic signal of said first polarity;
• an output;
• third means including first and second potential sources of differing magnitudes and of said first polarity;
• first semiconductor switch means coupled between said first potential source and said output;
• second semiconductor switch means coupled between said second potential source and said output;
• and
• means for causing said first and second semiconductor switch means to respectively couple the associated one of said first and second sources of potential to said output dependent upon the state of the logic signal received at said first means, for driving said medium with the data of said first logic signal between first and second values of a voltage of said first polarity;
• said second means being coupled to said third means to cause said third means to be disabled whenever said second logic signal is received at said second means;
• and
• fourth means coupled between said second means and said output for driving said medium with the data of said second logic signal between said first and second values of a voltage of the remaining polarity.