Interface providing impedance matching by selective connection of a resistor array to a power supply

An interface system for connecting a control circuit to a host computer wherein the control circuit has a plurality of input terminals and the host computer has a plurality of output terminals, said interface system comprising:

• a plurality of signal lines, each of said signal lines connecting one of the input terminals of the control circuit to a corresponding one of the output terminals of computer;
• a connector having a first terminal and a second terminal, said first terminal being connected to a power source, said connector including a short circuiting means for selectively connecting said first and second terminals together electrically;
• and
• a plurality of connection control means for impedance matching of the output of the host computer when said short circuiting means connects said first and second terminals, each of said plurality of connection control means having a first end and a second end, each said first end being connected to a respective one of said plurality of signal lines, each said second end being in electrical connection with said second terminal of said connector for connection to said power source to provide impedance matching for the output of the host computer when said short circuiting means connects said first and second terminals with said power source, said impedance matching not occurring when said short circuiting means does not connect said first and second terminals, each said connection control means including a means for preventing signal interconnection between ones of said plurality of signal lines.