A demarcating system for indicating the boundary 20 of an area 30 to an object 50 which has a receiver 101 for receiving electromagnetic signals. The system includes a control system 15, a wire loop 20, a signal generator 12, and current sensing circuitry 14. The wire loop can be arranged by a user along a path, so as to indicate the path to the object as part of a boundary of the area. The signal generator is electrically connected to the wire loop in order to apply voltage signals thereto, such signals causing the emission of corresponding electromagnetic boundary indicating signals from the wire loop that may be received by the receiver of the object. The signal generator is under the control of the control system with the voltage signals applied by the signal generator to the wire loop being controlled by the control system. The current sensing circuitry senses current signals present within the wire loop and the processors of the control system analyse such current signals. The processors of the control system are programmed to operate in a calibration mode whereby they: cause the signal generator to apply a series of test voltage waveforms to the wire loop, each of the test voltage waveforms generating a corresponding current waveform within the wire loop: and analyse the series of corresponding current waveforms, as sensed by the current sensing circuitry, so as to determine an operating voltage waveform that, when applied to the wire loop generates a corresponding operating current C I waveform that is substantially the same shape as a predetermined current waveform.
