Noise waveform analyzer was developed to measure the statistical distributions such as amplitude probability distributions of noise envelope. Using this system installed in a van, some statistical distributions of automotive radio noise in lower frequency microwave bands (1-3 GHz), received while driving on main streets and expressways in Tokyo, were measured to provide fundamental data for designing mobile communication systems in this frequency band. Variation of the impulse height, received in typical driving conditions, can be expressed by a log-normal distribution and impulse emission seems to be Poisson-distributed in time for time history records as long as 40 minutes.

Arc discharge at switching contacts is one of the key phenomena, because it strongly affects material wear/transfer, contact resistance and electromagnetic interference (EMI). The arc discharge is classified into various types from the viewpoint of its sustaining mechanism and voltage waveform. They are mainly steady arc, showering arc and initial arc. Furthermore, a steady arc consists of two stages named metallic phase arc and gaseous phase arc. In the metallic, phase arc, metal ious from the electrodes mainly sustain the arc. On the other hand, gas ions from the surrounding atmosphere play an important role in the gaseous phase. Each phase arc has different influence on contact performance and EMI. The purpose of this paper is to review the arc discharges at light duty electrical contacts, and to survey the effects of arc discharges on material transfer and EMI.