A CPU in a cellular phone counts the number of calling times in each area in which the cellular phone resides, and stores the number of calling times for each area. Each shoring panel having laterally on either end a vertical guide of circular cross section and lengthwise two identical cutting edges of triangular cross section, which are inversely arranged one on the top and the other at the bottom of panel and reverse relative to sidewall of excavation as well. A voltage on the data bitline being changed when a programmed non-volatile memory cell connected to an activated wordline couples the wordline voltage to the data bitline.