The R(t) function of the drift detector is reconstructed in the Fredholm in
tegral equation of the Ist type. Mathematical formalism is based on the ana
lytical expression of chi(2) at the point of the minimum of the trajectory
parameters (straight line and parabola) which is considered in statistical
generalization as a functional of R(t). The Monte Carlo examination and the
analysis of the experimental data for drift tubes are given. (C) 1999 Else
vier Science B.V.