A shielded cable is a data cable that has external protection to prevent electrical noise interfering with the signal being transmitted along the conductors, as well as to mitigate electromagnetic radiation to nearby devices. The shield protecting the twisted pair cable will reduce the detrimental effect of electromagnetic interference (EMI) to the signal. porta blindada
The types of shielded material for data cables commonly used are metallic shielding, such as aluminium or copper. The metallic shielding is designed to protect the signal from point A to point B to ensure the integrity of the signal. It is worth noting this is not to be confused with physical shielding which isn’t what we’re discussing here.
The twisted pair cable shielding are referred to as foil shielded or braided shielded, and been named according to industry and ISO/IEC 11801 standards. There are several variations of the shielded metal types and are abbreviated to be recognisable by acronyms, such as illustrated below:
U – unshielded
F – foil shielded
S – braided shielded
Sc – screened
TP – twisted pair
These abbreviations vary slightly between industry and ISO/IEC 11801 however internationally the abbreviations are commonly adopted by all involved. In addition, the forward slash are used to separate the outer shielded type description and the inner pairs shielding type description for self-explanatory reasons.
Each type of shielded material offers specific advantages. Therefore will suit a specific cabling installation scenario and would be carefully considered before job commencement to ensure the maximum benefits of the shielding is achieved.
There are numerous scenarios where utilising a shielded twisted pair cable would be beneficial. A shielded cable can enhance signal quality in computer networks especially when copious network cables are run in parallel, as well as, when there are electrical power cables nearby. Multiple cables run together will increase the likelihood of interference such as electromagnetic interference EMI.
Shielded cables can reduce alien crosstalk which is found between pairs of conductors. Furthermore there have been security concerns raised by IT security companies on alien-crosstalk potentially exposing sensitive data by this means. You’ll see shielded individual twisted pairs utilised to significantly reduce alien crosstalk in many organisations for added security that transmit sensitive data.
Shielded cables can transmit wider bandwidths that enhance throughput data rates. This is exactly what most consumers require with an ever evolving information highway online. The shielding of twisted pair cabling will also help maintain the distant from point A to point B to ensure optimal cable length is achieved.
In a typical networked computer desktop scenario there are numerous power cords powering the PC, monitor, UPS, printers, scanners and peripherals etc. An unshielded twisted pair cable could be unintentionally positioned near many electrical devices all potential causes of electromagnetic induction. Ideally there should be a minimum distant of 2 inches maintained between power and data cables. However a shielded cable would be more suitable in these scenarios.
Shielded cables are gaining popularity also since manufacturers have reduced the production costs, thus allowing cable resellers to sell shielded cables at reasonable prices. Especially CAT6 shielded patch leads available in multi-stranded core type are popular. The newer CAT6a shielded and CAT7 shielded cables are appearing gradually however are the preferred type.
Finally, a practical benefit is the outer shielding can be used as a form of grounding of the cable. Some manufacturers refer to it a.k.a special drain wire for grounding the connection at one end. The electrical noise created by EMI will travel along the outer shielding and will be grounded.