An aircraft moveable element monitoring system (100, 200) comprising: a signal generator; a signal transmitter coil electrically connected to the signal generator; a signal detector; a signal receiver coil electrically connected to the signal detector; and one or more moveable element signal transmission units (115a, 115b, 115c), wherein each moveable element signal transmission unit comprises a first signal transmission unit coil (116a, 116b, 116c) and a second signal transmission unit coil (118a, 118b, 118c), the first signal transmission unit coil being electrically connected to the second signal transmission unit coil; wherein: each moveable element signal transmission unit is configured to be installed on a respective moveable element (106, 106a, 160b, 106c) of an aircraft the signal transmitter coil, the one or more moveable element signal transmission units and the signal receiver coil form an inductively coupled transmission line; the signal generator is configured to provide an electrical signal to the signal transmitter coil and the signal detector is configured to detect the electrical signal via the signal receiver coil; the signal detector is configured to determine a condition of one or more moveable elements by comparing the detected electrical signal to a predetermined signal characteristic; wherein the predetermined signal characteristic includes at least one of: a peak voltage; a peak root mean squared voltage; a voltage profile over time; an original phase of the electric signal produced by the signal generator. a signal generator; a signal transmitter coil electrically connected to the signal generator; a signal detector; a signal receiver coil electrically connected to the signal detector; and one or more moveable element signal transmission units (115a, 115b, 115c), wherein each moveable element signal transmission unit comprises a first signal transmission unit coil (116a, 116b, 116c) and a second signal transmission unit coil (118a, 118b, 118c), the first signal transmission unit coil being electrically connected to the second signal transmission unit coil; wherein: each moveable element signal transmission unit is configured to be installed on a respective moveable element (106, 106a, 160b, 106c) of an aircraft the signal transmitter coil, the one or more moveable element signal transmission units and the signal receiver coil form an inductively coupled transmission line; the signal generator is configured to provide an electrical signal to the signal transmitter coil and the signal detector is configured to detect the electrical signal via the signal receiver coil; the signal detector is configured to determine a condition of one or more moveable elements by comparing the detected electrical signal to a predetermined signal characteristic; each moveable element signal transmission unit is configured to be installed on a respective moveable element (106, 106a, 160b, 106c) of an aircraft the signal transmitter coil, the one or more moveable element signal transmission units and the signal receiver coil form an inductively coupled transmission line; the signal generator is configured to provide an electrical signal to the signal transmitter coil and the signal detector is configured to detect the electrical signal via the signal receiver coil; the signal detector is configured to determine a condition of one or more moveable elements by comparing the detected electrical signal to a predetermined signal characteristic; wherein the predetermined signal characteristic includes at least one of: a peak voltage; a peak root mean squared voltage; a voltage profile over time; an original phase of the electric signal produced by the signal generator.