Study of e+ e- --> WW --> Lepton Neutrino q qbar at 500 GeV

W-pair production in e+ e- annihilation at 500 GeV is studied using different Monte Carlo generators and the proposed detector for the Linear Collider in its TESLA version. Semileptonic W decays are used to give hints for the detector optimization and to determine the expected accuracy of the W mass determination and the measurement of the anomalous triple gauge boson couplings. With an expected luminosity of 50 inverse fb a W mass measurement with an accuracy of 15 MeV should be possible. The triple gauge boson couplings can be determined with an accuracy in the order of ten to minus three.