Verfahren und System zum übertragen von Energie und Daten

In a process for the transfer of energy from a main unit to a secondary unit and for the bidirectional transmission of data between the said units, energy in the form of an a.c. supply signal of a predetermined frequency is transferred from the main unit to the secondary unit. The a.c. supply signal generates a clock signal which causes the transfer of a first data signal from the main unit to the secondary unit, the generation of a time window in the secondary unit on receipt of the first data signal based on a time base determined by the clock signal, the number of oscillations of the first data signal within the time window is counted and the transmitted first data value is thus determined, whereupon a second data signal is transferred back from the secondary unit to the main unit.