A system is provided for determining the position of an implanted device (10) in a human or animal body relative to a probe (12). In one device, a reference signal is generated and it is received in the other device. A phase angle or an amplitude attenuation or difference between the reference signal and the received signal is used to determine the proximity of the probe to the implanted device. The approach makes use of body channel sensing by which the frequencies at which the body behaves as a waveguide are employed.
