Abstract: An apparatus or system for identifying a conduit, having a flexible wall, and comprising at least one open end. The apparatus or system has a gas pressure signal generator for applying a pressure signal at the open end of the conduit to be identified to cause the conduit to be subjected to an increase in internal gas pressure. At least one sensor is provided for measuring, at a measuring location remote from the open end, at least one of the following variables a) width of the conduit, b) diameter of the conduit, c) temperature of the conduit wall, d) load on the conduit wall, and e) strain on the conduit wall. The conduit is identified when the sensor(s) detect(s) a change or changes in the variable(s) experienced by the conduit so identified in response to the gas pressure signal.