Patent ID: 6523070
Filing Date: 2003-02-18
Classification: G06F

Abstract:
A network communication device comprising a plurality of ports whereby connection can be made to network equipment and connection means arranged to enable connection to two other similar devices whereby a plurality of said devices may be cascade connected, the device comprising sensing means arranged to sense whether the device is at the end of a series of cascade connection devices, said sensing means comprising:first and second complementary circuitry providing first and second outputs respectively and having first and second interconnections respectively, the first and second circuitry being arranged whereby said first output has a first value in the event that said first interconnection is connected to a second interconnection in another device and a second value if it is not so connected, and whereby said second output has a first value in the event that said second interconnection is connected to a first interconnection in another device and a second value if it is not so connected; and means arranged to indicate that said device is at the end of a series of cascade connected devices when one of said first and second outputs takes its second value; wherein said first circuitry comprises means arranged to drive said first interconnection to a first logical level and said first output to take said first value for said second value, dependent on whether current is drawn via said first interconnection, and said second circuitry comprises means arranged to pull said second interconnection to a second logical level and to sense when said second interconnection is driven to said first logical level; whereby connection between said second circuitry in one device and said first circuitry in other device provides an active signal to said first circuitry of said other device and causes a current driver in series with a resistor in said second circuitry of said one device to drive current through said resistor providing an output of logical level dependent on current flow through the resistor.