Below is a list of EMI Shielding manufacturers from Foothill Ranch, California. EMI shielding is an enclosure, coating or transmitted signal which protects electronic equipment from ambient electromagnetic interference. EMI, or electromagnetic interference, is the magnetic field which is created by electrical currents; EMI can travel along wires, electrical circuits and conductors, while radio frequency interference (RFI) is radiated electromagnetic “noise” which travels through the air as radio waves. Both EMI and RFI cause the same effect.