An experimental procedure for studying and analyzing conductance G of the inversion channel as a function of transverse voltage Vg (the field effect) and longitudinal voltage Vd is developed for metal/oxide/semiconductor (MOS) structures. The presence of a quasi-plateau in dependence G(Vg) at G ≈ 2e2/h and a dip in dependence G(Vd) at |Vd| ≤ 100 mV with a minimum at Vg = 0 are demonstrated by using the example of mesoscopic Si-MOS structures with an inversion p-type channel and an increased concentration of embedded charges at 77 K. The effective energy parameters of quantum contacts formed in the saddle-point regions of the fluctuation potential are determined. The experimental accuracy obtained allows the use of regularizing algorithms for consideration of the effect of the final temperature.