A relay device (201) is described for relaying radio frequency signals received from an antenna implanted within a patients body to another device located outside the patients body, the relay device comprising a first slot antenna for detecting radio frequency signals sent from the antenna implanted within the patients body and a second slot antenna for transmitting radio frequency signals to the other device located outside the patients body, whereby the first and second slot antennas comprise elongated slots (209, 211) on opposite sides of a cavity (203). The signals to be transmitted by the second slot antenna are to be used to relay information conveyed by the signals detected by the first slot antenna. The relay device also comprises switching means (215, 217) for switching the first and second slot antennas between active and inactive configurations.
