An implantable medical device including a data communication device that includes a device to alter and/or generate an oscillatory electric field imposed on body tissue surrounding the implantable medical device when the implantable medical device is in its implanted state. The device that alters an oscillatory electric field modulates an impedance of body tissue surrounding the implantable medical device when the implantable medical device is in its implanted state and within an oscillatory electric field. The device that alters an oscillatory electric field includes a device that generates an oscillatory electric field that is phase-synchronized with an oscillatory electric field imposed on body tissue surrounding the implantable medical device when the implantable medical device is in its implanted state.