COMMUNICATING ACROSS GALVANIC ISOLATION

Signal transmission circuitry comprises a conductive transmitting coil, a first power supply, a semiconductor switch to reversibly couple the transmitting coil to the first power supply, control circuitry to control the coupling of the transmitting coil to the first power supply by the semiconductor switch, a second power supply coupled to supply power to the control circuitry and a unidirectional current flow path configured to allow current to flow from the first power supply to the second, power supply for the first power supply to supply power to the second power supply.