Shielded vs. unshielded cables
The environment determines whether cable should be shielded or unshielded. Quiet office environments, busy retail establishments, and individual workshops all require different levels of shielding.
Shielded cable with PVC jacket, foil braid, aluminium shield, and individually shielded conductors.
Unshielded cable with PVC jacket.
Shielding is the protective sheath surrounding and protecting the wires of the cable from electromagnetic leakage and interference. This electromagnetic (EMI) activity is commonly referred to as noise. Sources of EMI in the workplace include lift motors, fluorescent lights, generators, compressors, air conditioners, and photocopiers.
Foil-shielded and Copper-shielded
To protect your data in a noisy area (with high EMI), choose a shielded cable. Foil is the most basic cable shield, but a copper-braid shield provides more protection.
Use a foil-shielded cable in busy office or retail environments. For industrial environments, you may want to choose a copper-braid shield. For quiet office environments, choose unshielded cable.
Plastic and Metal Hoods
Hoods (the protective enclosure housing the connectors and covering the pinning) are either metal or plastic. Metal hoods offer protection against electromagnetic interference (EMI) and radio-frequency interference (RFI) at the termination point on the connector shell.
Generally, you should choose metal hoods when using shielded cable and plastic hoods with unshielded cable.
More about Shielded Ethernet Cables.