The Cable Avoidance Tool (CAT) is used to detect the signal generated by the signal generator (Genny). The Genny is placed at the end of a duct rod and pushed through a duct, then when the blockage is reached the CAT is used to detect its location and hence valuable time is saved. Also can be used when the route of a duct is not plotted, simply use the CAT to follow the route of the Genny plotting as you go.