Below is a list of Electromagnetic Shielding manufacturers from Ayer, Massachusetts. Electromagnetic shielding is a barrier which protects electronic equipment from ambient electromagnetic interference. Electromagnetic interference, or EMI, 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 similar effects, although EMI typically operates on lower frequencies than RFI.