Addressable open connector test circuit

In an open circuit detection apparatus for detecting whether a connection is closed between a local node and a remote node, the remote node having a known impedance, the apparatus having a ping source connected to the local node, the ping source having an output for transmitting an address unique to the remote node and an input for sensing the impedance of the remote node, a test circuit for effecting a change in the known impedance of the remote node, the test circuit comprising:

• an address decoder for receiving the address from the output, said address controller having a unique address;
• a control signal, said address decoder asserting said control signal upon the address matching said unique address of said address decoder;
• and
• an impedance varying device being responsive to said control signal, said impedance varying device effecting a change in the impedance of the remote node, said change indicating to the input that the connection is closed.