Abstract: A system for testing concealed ducts including a pull cable and a transmitter, the transmitter including a transmission means for emitting radiation disposed at one end of the pull cable and at least one electric wire disposed inside the pull cable, wherein the electric wire or wires enables electrical connection between the transmitter and the transmission means, and a receiver for receiving signals from the transmission means and for indicating strength of the received signals. The scope of the invention includes methods of finding blockage within a conduit pipe and finding the path of a conduit pipe, built into a partition, by inserting a pull cable into a conduit pipe and detecting the location of the front end of the pull cable.