Detailed description: General
A bus is the leads over which information is sent digitally and serially. Digital means that the signal is either 1 or 0. Serial means that the information is sent in "packages" in close succession.
All the control modules in the car are connected via three buses. Two of these buses are electrical while the third is optical.
The two electrical buses are the P-bus (Powertrain bus) and I-bus (Instrument bus). The P-bus has two leads and the I-bus one lead.
The difference in voltage between the two leads (P-bus) or the lead and ground (I-bus) is either 0 V or roughly 5 V. The information is coded so that different combinations of pulses, with the values 0 V and 5 V, have different meanings.
The optic bus is known as the O-bus and has an extremely high capacity. It is primarily used to send audio signals, e.g. from the radio receiver or CD changer to the amplifiers. Digital information is transmitted in a plastic cable by pulsating the sound at low and high intensities to thereby form ones and zeros.