A network diagnostic device is disclosed that digitally samples the
voltages on the cabling of the network, but does so at a much higher rate
and with greater resolution then is required to minimally detect digital
transmissions on the cabling. This sampling provides information on the
analog characteristics of digital, noise, and interference signals on the
network. Thus, network problems can be precisely diagnosed. The device
includes a fast digitizer with a long memory and a system processor that
statistically analyzes the signal events captured by the digitizer. The
invention is also capable of performing time domain reflectometry (TDR)
analysis of a functioning network. This is accomplished by placing a TDR
signal on the network surrounded by a transmission that the network
devices will interpret as a broadcast diagnostic packet. This will cause
the network nodes to ignore the transmission. The digitizer, however, is
able to detect the networks response to the TDR signal. Methods for
identifying unknown network sources and Manchester decoding are also
disclosed.
