(EN) A system for externally locating the depth and orientation of a catheter (9) in tissue with an external probe (12) which generates a virtual rotating magnetic field. The catheter (9) includes an inductive coil (30) for developing an induced signal in response to the virtual rotating magnetic field. An indicating device (6) such as a light bar display or digital readout indicates the strength of the induced signal for locating, independently of the relative angular orientation of the probe and the catheter, the depth in the tissue of the catheter.