A data logging system and method in which an implantable medical device
transmits logged data to an external data logging device with low energy
potential signals. The implantable device generates potential signals
modulated with digitally encoded data by operating a current source to
cause corresponding electrical potentials that can be sensed at the skin
surface by the external data logging device. The data logging device then
demodulates the sensed potentials to derive the digital data and stores
the data in a data logging storage medium.