A device for detecting and compensating field distortion in underground line locators by means of mapping the field-strength of the field generated by electrical currents within the buried line. The data’s source or destination need not be considered in determining where to buffer the data. First horizontal sections extend horizontally forward from the lower ends of the first vertical leg sections, and are rotatably connected to a first slider which is slidably connected to a fixed rail. This second variable serves to control operating parameters of the internal combustion engine in an open-loop andor a closed-loop manner. R4 an aliphatic bridge with a main chain having 1 to about 20 carbon atoms, an alicyclic bridge, an aromatic bridge, an arylaliphatic bridge or an arylalicyclic bridge, comprising 0 to about 3 heteroatoms independently selected from the group consisting of N, O, S, Se and Si, and X is halogen.