  We study the sensitivity of the processes `e+ e- -> lepton (l) neutrino (v)
quark (u) antiquark (d)', where the lepton is an electron or a muon, on the
non-standard trilinear gauge couplings (TGC), using the optimal observables
method at Linear Collider energies. Our study is based on the four-fermion
generator ERATO. Taking into account all possible correlations between the
different trilinear gauge coupling parameters, we show that they can be
measured with an accuracy of $10^{-3}$ to $10^{-4}$ for typical Linear Collider
energies and luminosities.
