Electro-magnetic Interference. Stray electro-magnetic fields generated from any current-carrying conductor such as nearby motors, switching controllers, high-power contactors, etc. which cause a brief, intense pulse that often couples into low-level signal circuits causing noise. This interference can enter either directly into the signal path, or indirectly via the power or ground connection. High-power RF transmitters can cause similar effects, called RFI. See induction.