The generation of an activity display for displaying history data for one or more migration values is provided. The method involves using a model of a body, wherein the device is placed in proximity to the model and the electric field is measured at discrete points, including measuring the magnitude of the electric field at points of a first and a second surface of the model. The coupling body includes a first end with a threaded section and a first surface adapted to press against a first set of electrical connector wedges. The feedback means is coupled to the voltage conversion means and a current sensing means and provides a feedback signal to the voltage conversion means that is indicative of the voltage drop across the current sensing means which thus represents the current flowing through the load. Indicia typical of signs held by school crossing guards are disposed on all the planar surfaces of the planar sign panels, and a slotted top end cap is engageable with the top horizontal edges of the planar sign panels.