The equivalence conditions between a general linear and non-autonomous two-port, having two access gates ((1), (1') and (2), (2')) and an inner port ((3), (3')) and a linear and non-autonomous, in a restricted sense two-port are established, in harmonic steady-state. This equivalence, permits to attach to any such a general, linear and nonautonomous two-port an equivalent linear and non-autonomous, in restricted sense, two-port but not inversely.

Keywords: General linear and non-autonomous two-port (GLNT), Linear and non-autonomous in restricted sense two-ports (LNRST), Equivalence.