aegis
Ferrites
Most ferrites function at frequencies between 1 KHz. to 1 GHz. and it is important to understand that cellular phones operate at frequencies above 1 GHz. Ferrites are commonly used on 50 to 60 Hz. AC power cords and in the circuitry of electronic equipment to prevent unwanted outside radiation frequency interference (RFI), also known as noise, from penetrating the wire and interfering with other components within the equipment.
Ferrites are not designed, or intended, to be near the body and are never used for shielding people because their electromagnetic absorption properties are significantly affected by environmental and operating conditions, including temperature, pressure, field strength, frequency and time. They do not provide any protection whatsoever from cellular phone radiation when using a headset because they can only prevent radiation frequencies between 1 KHz. to 1 GHz. from entering the wire, thus having no effect upon the frequencies traveling up the wire from a cellular phone.
Ferrites are widely used in the electronics industry because in addition to their low cost (less than US $1.00), they also offer high magnetic permeability which concentrates and reinforces the magnetic field and high electrical resistance which limits the amount of electric current flow in the ferrite. Their specifications are always presented as resistance (in OHMS) and since they cannot limit the amount of radiation flow, they are never used for any applications where a stringent degree of component radiation shielding effectiveness is required.
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