Since the derivation of the in-loop full⁃zone voltage response formula, many papers have dealt with utilizing it to work out the solution for full⁃zone apparent resistivity, and the conclusions have three points: unique valued, dual⁃valued and undefined valued. The conclusions are based on mathematical theoretical analysis. They are of course correct, but not perfect. The main characteristic of the full⁃zone apparent resistivity curve of observed data is continuous or discontinuous. Based on model study, the author concluded that the main characteristics of an observed data on he layered earth are as follows: the full⁃zone apparent resistivity curves are all discontin⁃uous, and there are three factors, i.e., no unique value exists because measurements are discontinuous, and therefore sampling time is rarely just at the transition point; undefined value exists because observed value is greater than homogeneous half⁃spaces; wrongly de⁃fined value exists when the observed response is lower than homogeneous half⁃space's. The last term is named by the author firstly. The normalizing processing is the only method to get the continuity of the full⁃zone apparent resistivity.%自中心回线全区电动势响应推导得出后，发表了很多用它求解全区视电阻率特性的文章，总结的特点为：唯一解、双解及无解。它是纯数学理论结果，正确无误，然而并不全面。笔者认为层状大地实测数据求全区视电阻率特征的要点在于曲线的连续性。笔者根据模型研究认为层状大地的曲线都是不连续的，因为无唯一解，在转换点两侧的左右支不是无解就是偏解。因为实测层状大地的数据是非连续采样读取，极少可能正在转换点上，所得响应值大于理论值则无法求得视电阻率（无解），若低于理论值虽可求得视电阻率值，但其值并不正确，笔者命名此特征为“偏解”。“偏解”特征为以往所忽略，为使全区视电阻率曲线连续，采用归一法求全区视电阻率是一个合适的方法。
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