Technician Handbook ! 673 Electronic & Computer Controlled Systems Electronic Communication Electronic and computerized components communicate with each other using electrical signals. Signals can be as simple as the presence or absence of voltage or current on a wire (ON/OFF signal). Signals can also be as complex as a series of 64 voltage pulses (bits) in a data packet containing precise instructions for a receiving ECU to execute. In all cases, it is changing voltage that contains the information for controlling electronic components. When changing voltage is displayed on a graph of voltage versus time, the resulting pattern is called a waveform.
Types of Waveforms Electronic circuits produce many different common waveforms. Voltage smoothly changing between a low and a high value produces a sine wave . It is often a change in the signal’s amplitude or frequency that conveys information. A square wave is a digital version of a sine wave. (Digital circuits typically just turn voltage on or off instead of smoothly changing voltage the way analog circuits do.) When voltage changes momentarily and then returns to a steady state again, the result is a single pulse . A square wave can be viewed as a repeating sequence of voltage pulses. Any sequence of pulses may be referred to as a pulse train .
Audio and video signals appear as randomly changing voltage. Data packets flowing between ECUs also appear as random signals. These types of signals produce non-repeating patterns . 24 Technical Training