Consequently, the converter 14 is preferably a laser, light-emitting diode or edge-emitting diode 18 when used to transmit a signal including data from the electrical system 16 or the converter 14 is preferably a photo diode or photo transistor 15 when used to transmit a data signal into the electrical system 17, as shown in FIG. 8A. Thus, the converter 14 is essentially a photo-optical device and