Abstract: A communications extension link for use between a computer and a keyboard and display unit has at the computer site a first interface circuit connected to it and adjacent to the keyboard and display unit a second interface circuit connected to it. The two interface circuits may then be spaced serveral hundred feet by an extension cable. The first interface circuit includes capacitors connected between keyboard data and clock lines and a positive supply terminal, and buffer amplifiers are placed in the signal lines relating to the display unit. The second interface circuit employs discrete resistors between clock and data lines and the positive supply terminal, and between the vertical sync line and logic ground. In addition, capacitance is added between the positive supply terminal and logic ground.