How do contact tracing systems differ between NSW and Victoria?

Outbreaks of coronavirus are growing in Victoria and New South Wales, and in Queensland health authorities are testing people in several cities. At the heart of the investigations are teams of contract tracers, who help track down contacts of all COVID positive cases. A lot has been said over the last few months about how New South Wales' system is the "gold standard" that Victoria should follow. So on today's Coronacast, how do the systems in the two states differ? And how do contact tracers work?