Computer Telephony (CT)

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Computer telephony integration, also called computer–telephone integration or CTI, is a common name for any technology that allows interactions on a telephone and a computer to be integrated or coordinated. The term is predominantly used to describe desktop-based interaction for helping users be more efficient, though it can also refer to server-based functionality such as automatic call routing.

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    TP = twisted pair

    U = unshielded

    F = foil shielding

    S = braided shielding 
     
     
     

    Most common cable categories 

Category Type Frequency Bandwidth Applications Notes
Cat1   0.4 MHz Telephone and modem lines Not described in EIA/TIA recommmendations. Unsuitable for modern systems.[5]
Cat2   ? MHz Older terminal systems, e.g. IBM 3270 Not described in EIA/TIA recommmendations. Unsuitable for modern systems.[5]
Cat3 UTP[6] 16MHz[6] 10BASE-T and 100BASE-T4 Ethernet[6] Described in EIA/TIA-568. Unsuitable for speeds above 16 Mbit/s. Now mainly for telephone cables[6]
Cat4 UTP[6] 20MHz[6] 16 Mbit/s[6] Token Ring Not commonly used[6]
Cat5 UTP[6] 100MHz[6] 100BASE-TX & 1000BASE-T Ethernet[6] Common in most current LANs[6]
Cat5e UTP[6] 100MHz[6] 100BASE-TX & 1000BASE-T Ethernet[6] Enhanced Cat5. Same construction as Cat5, but with better testing standards.
Cat6 UTP[6] 250MHz[6] 1000BASE-T Ethernet Most commonly installed cable in Finland according to the 2002 standard. SFS-EN 50173-1
Cat6e   250MHz (500MHz according to some) Not a standard; a cable maker's own label.  
Cat6a   500MHz 10GBASE-T Ethernet ISO/IEC 11801:2002 Amendment 2.
Cat7 S/FTP[6] 600MHz[6] Telephone, CCTV, 1000BASE-TX in the same cable. 10GBASE-TEthernet. Four pairs, U/FTP (shielded pairs). Standard under development.
Cat7a   1000MHz Telephone, CATV, 1000BASE-TX in the same cable. 10GBASE-TEthernet. Four pairs, S/FTP (shielded pairs, braid-screened cable). Standard under development.
Cat8   1200MHz Under development, no applications yet. Four pairs, S/FTP (shielded pairs, braid-screened cable). Standard under development.
 

Advantages 

  • It is a thin, flexible cable that is easy to string between walls.
  • More lines can be run through the same wiring ducts.
  • UTP costs less per meter/foot than any other type of LAN cable.
  • Electrical noise going into or coming from the cable can be prevented.[7]
  • Cross-talk is minimized.[7]
 

Disadvantages 

  • Twisted pair’s susceptibility to electromagnetic interference greatly depends on the pair twisting schemes (usually patented by the manufacturers) staying intact during the installation. As a result, twisted pair cables usually have stringent requirements for maximum pulling tension as well as minimum bend radius. This relative fragility of twisted pair cables makes the installation practices an important part of ensuring the cable’s performance.
  • In video applications that send information across multiple parallel signal wires, twisted pair cabling can introduce signaling delays known as skew which results in subtle color defects and ghosting due to the image components not aligning correctly when recombined in the display device. The skew occurs because twisted pairs within the same cable often use a different number of twists per meter so as to prevent common-mode crosstalk between pairs with identical numbers of twists. The skew can be compensated by varying the length of pairs in the termination box, so as to introduce delay lines that take up the slack between shorter and longer pairs, though the precise lengths required are difficult to calculate and vary depending on the overall cable length.

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