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An electric “fence” without fencing has been developed jointly by the
Australian Departments of Agriculture and Environment (WO 00/57692). A radio
mast in the middle of a wide open space sends out a signal in all directions.
The cattle each have a radio receiver around their neck, connected to electrodes
in their nostrils. If the animals move too far from the transmitter, where the
signal is weaker, the receiver first sounds a warning tone and then administers
a tingling electric shock. The animals soon learn not to move far from the
transmitter, which effectively fences them in.