2. Principles
Every electrical device emits and receives electromagnetic disturbances. Therefore, usually, every device is both source and sink as depicted in Figure 1. However, due to the performance of these devices, some of them are more likely to be a significant source, and some are prone to be a sink. A pacemaker, for example, is more likely to be a jamming sink than a source.
There are two ways to emit or receive disturbances. The first one is through free space; no medium is necessary. Mobile phones use this phenomenon to operate. They emit encoded electromagnetic waves and also receive and decode electromagnetic waves to send and receive information. However, electromagnetic waves are not the only ones that take this path; electric and magnetic fields can also spread and couple into a device.
The second way a disturbance can take is over a wire, a metal sheet, or basically anything that is conductive. Just as with radiated emissions, several types of disturbances may occur.