  Some basic properties of nonradiating systems are considered. A simple
connection is established between the existence of residual electromagnetic
potentials and the current density spectrum of the system. The properties of
specific configurations based on toroidal and supertoroidal currents are
modeled with the finite-difference time-domain method. Possible applications
are discussed. A design of a new type of nonradiating system, based on a
left-handed metamaterial is proposed and the system performance is modeled
numerically.
