A sleep apnea treatment device, comprising: a primary antenna configured to be located external to a subject, at least one processor configured for electrical communication with the primary antenna, the at least one processor configured to: cause transmission of a primary signal from the primary antenna to an implantable device implanted in the subject on a genioglossus muscle proximal to a hypoglossal nerve of the subject, wherein the implantable device includes at least one pair of modulation electrodes, wherein the processor is further configured to adjust one or more characteristics of the primary signal to generate a sub-modulation control signal adapted to cause a current at the at least one pair of modulation electrodes below a neuromuscular modulation threshold of the hypoglossal nerve when received by the implantable device and to generate a modulation control signal adapted to cause a current at the at least one pair of modulation electrodes above a neuromuscular modulation threshold of the hypoglossal nerve when received by the implantable device, characterised in that the at least one processor is further configured to receive via the primary antenna, a condition signal from the implantable device in response to the sub-modulation control signal, wherein the condition signal is indicative of tongue movement. a primary antenna configured to be located external to a subject, at least one processor configured for electrical communication with the primary antenna, the at least one processor configured to: cause transmission of a primary signal from the primary antenna to an implantable device implanted in the subject on a genioglossus muscle proximal to a hypoglossal nerve of the subject, wherein the implantable device includes at least one pair of modulation electrodes, wherein the processor is further configured to adjust one or more characteristics of the primary signal to generate a sub-modulation control signal adapted to cause a current at the at least one pair of modulation electrodes below a neuromuscular modulation threshold of the hypoglossal nerve when received by the implantable device and to generate a modulation control signal adapted to cause a current at the at least one pair of modulation electrodes above a neuromuscular modulation threshold of the hypoglossal nerve when received by the implantable device, characterised in that the at least one processor is further configured to receive via the primary antenna, a condition signal from the implantable device in response to the sub-modulation control signal, wherein the condition signal is indicative of tongue movement. cause transmission of a primary signal from the primary antenna to an implantable device implanted in the subject on a genioglossus muscle proximal to a hypoglossal nerve of the subject, wherein the implantable device includes at least one pair of modulation electrodes, wherein the processor is further configured to adjust one or more characteristics of the primary signal to generate a sub-modulation control signal adapted to cause a current at the at least one pair of modulation electrodes below a neuromuscular modulation threshold of the hypoglossal nerve when received by the implantable device and to generate a modulation control signal adapted to cause a current at the at least one pair of modulation electrodes above a neuromuscular modulation threshold of the hypoglossal nerve when received by the implantable device, characterised in that the at least one processor is further configured to receive via the primary antenna, a condition signal from the implantable device in response to the sub-modulation control signal, wherein the condition signal is indicative of tongue movement. <EOS>