Data transmission system

• There are 6 main types of cable available for data networking

  • Unshielded twisted pair-UTP (conduit) 
  • Shielded twisted pair-STP (conduit)
  • Screened twisted pair SCTP (conduit)
  • Coaxial
  • CAT5
  • Fibre optic
• For ELV what voltages do AC and DC run on

  AC = 0-50v

  DC = 0-120v
• Voltage Band I is defined as levels of voltage which are too low to provide serious electric shocks; effectively this limits the band to ELV. 
• BS7671, prohibits Band I and Band II cables sharing the same cable enclosure or multi core cable unless: every cable is insulated for the highest voltage present or be segregated by space or is in a separate containment
• Circuits the run on Band I voltages include Telecommunications, data transmission, signalling, sound systems. alarm circuits, bell and call systems
• What does UTP stand for


  Unsheathed Twisted Pair
• what does LAN stand for


  Local Area Network
• • UTP cable came into use in LANs with the introduction of Ethernet
  • Ethernet allows many different devices to connect to the network, and is a communications system that enables data to be managed without crashing the system
• What does STP stand for


  Shielded Twisted Pair
• STP cable can carry a wider range of frequencies than UTP and is less affected by external electromagnetic sources
• What is needed to guarantee minimum electromagnetic interference from other sources the STP cable

  • Have the shield electrically continuous for the whole length
  • All components must be shielded so no mixing of UPT and STP
  • The shield must enclose both the twisted pair and the core
  • The shield must be earthed at each end
• What does Sctp stand for


  Screen twisted pair
• • Sctp cable is a combination of UTP and STP.
  • The foil shield is earthed and is surrounds all four pairs of twisted pairs. Effectively we have STP shielding four unshielded pairs, this allows for the cable to reduce in size
• Most new installations are currently installed with category 6 UTP cabling components:

  • RJ45 Sockets
  • RJ45 Plugs
  • Cat5e path panels

  Termination method for RJ45 outlets is insulation displacement

  note: CAT5E data cable runs shall not exceed 100m, as this would weaken the data cable
• • The fibre optics is the optical quality plastic core is essentially a mirror wound into a thin tube. 
  • Light rays are modulated into digital pulses with a laser, move along the core without penetrating the cladding 
  • The light pulses stay within the fibre optic cable because of a scientific principle known as "total internal refraction' 
  • The laser light bounces down the cable and when it strikes the inner wall it is always deflected inwards and, therefore, does not escape out of the cable. 
  • The minimum bending radius is 15× the diameter 
• The process of what goes through the fibre optic cable

  
• • Single mode Fibre Optic cable is used for both interbuilding and intrabuilding backbone cable
  • At distances up to 3km, single mode fibre will deliver data rates up to 10 Gbps with a bandwidth of 20Gbps
  • Its operating wavelengths are 1310nm and 1550nm
  • The fastest single-fibre links in commercial operation top out at 100Gbps
• Coaxial, is primary used for audio and visual purposes, especially television, cable TV, satellite and HD digital video applications
• There's three main types of coaxial cable and they differ in size shielding and screening techniques


  • RG59/U Coaxial Cable
  • RG6U satellite Cable, Aluminium Braid, Black PVC Jacket
  • RG11 Dual and Quad Shielded Coax
• The advantages and disadvantages

  Advantages

  • Greater data transfer
  • No electric indifference

  Disadvantages

  • the equipment is expensive
  • The minimum bending radius is x15 the diameter of the cable
• What is Ethernet cable used for

  • Connecting to the network
  • Making sure that the data in the communication systems does not crash
• What are MHz of each of the Cat cables

  • Cat 5e can take a maximum bandwidth of 100M Hz  
  • Cat 6 is capable of 400 MHz 
  • Cat 7 is capable of 625 MHz. 
  • Cat 8 is capable of up to 1400 MHz. 
  • Cat 9 is referred to as 1.2 GHz cable  
  • It is not recommended to exceed 100m for a single lengths of Cat cable without signal re-amplification
• What is the sequence of the fibber optic


  1. Input data
  2. Transmitter circuitry
  3. Light source
  4. Detector
  5. Receiver circuitry
  6. Output data