Apparatus comprise a photovoltaic cell arrangement having a front surface and a rear surface, and first and second conductor patterns formed on different ones of the front and rear surfaces. The first conductor pattern comprises at least one loop, and the apparatus comprises at least a first terminal connected to the second conductor pattern, and second and third terminals connected to different ends of the at least one loop of the first conductor pattern. A transducer arrangement comprises a transducer body having a front surface and a rear surface, and first and second conductor patterns formed on different ones of the front and rear surfaces. The first conductor pattern comprises at least one loop. The transducer arrangement comprises at least a first terminal connected to the second conductor pattern, and second and third terminals connected to different ends of the at least one spiral loop of the first conductor pattern. The transducer body and the first and second conductor patterns together form a photovoltaic transducer arrangement and the second conductor pattern constitutes an induction transducer.