Telecommunications Cables and Network Technologies

Posted on Jan 13, 2025 in Computer Engineering

Telecommunication Cables and Network Technologies

Types of Cables

  • Dual Pair Parallel Cable: Consists of two parallel cables, often rigid, isolated by a plastic such as polyethylene. It is used to connect the cable modem, telephone, or rosette.
    • Inconvenience: Susceptible to noise and electromagnetic interference, as the part that carries the signal can act like an antenna.
  • Twisted Pair Cable: Minimizes electromagnetic interference. The two wires are twisted, canceling out the effects of sending and receiving signals from other conductors. Used in PBXs to connect the subscriber to a local telephone exchange.
    • Disadvantages: Limited transmission speed and bandwidth.
    • Features: Three types of classes, depending on the shielding. Shielding minimizes external interference and decreases attenuation.
    • UTP (Unshielded Twisted Pair): Small, lightweight, flexible, cost-effective, and has a variety of suppliers.
    • FTP (Foiled Twisted Pair): Heavier, reduces interference, but is difficult to manipulate.
    • STP (Shielded Twisted Pair): Significantly reduces interference, but is heavy and rigid. Used for voice and data transmission in industrial facilities.
  • Coaxial Cable: A metallic transmission medium that has two conductors separated by a dielectric. Eliminates external electromagnetic interference.
  • Fiber Optic: Medium with a large bandwidth. Emits electromagnetic waves in the visible light spectrum.
    • Advantages: High capacity, higher bandwidth, greater link distances, total immunity, less attenuation, less weight and size, but difficult to manipulate.
    • Singlemode: Core diameter less than 10µm and a cover of 125µm.
    • Multimode: Diameter of 50, 62.5, or 100 micrometers.

RTB (Switched Telephone Network)

A circuit-switched network with a star topology. Each user connects via a subscriber loop to the central office.

Types of Calls to a Central Switch

  • Local calls
  • Outbound calls
  • Inbound calls
  • Transit calls

The solution is frequency division multiplexing (FDM), which modulates each 4KHz channel to a different carrier frequency. The number of channels that can be sent over each link depends on the channel capacity (30 in Europe, 24 in the U.S.).

Telephone Installation

  • Base Unit: The part of the terminal where the keyboard and electronic circuitry are located. It processes the voice signals of each interlocutor.
  • Handset: Contains the microphone and speaker, allowing us to establish voice conversations.
  • Spiral Cables: Connect the handset to the base unit (4 wires).
  • Two-Wire Telephone Cable: Connects to the user’s telephone power supply or telephone rosette, which connects to the telephone line.

Cordless Telephone

Uses the DECT (Digital Enhanced Cordless Telecommunications) standard.

Features

  • Transmission of electromagnetic waves (20MHz frequency band).
  • 10 carriers (each using GFDK modulation, each carrying 12 channels, for a total of 120 channels).
  • Maximum range of 50m (indoors) and 300m (outdoors).

ISDN (Integrated Services Digital Network) (2B+D)

  • 3 channels (2 for voice and 1 for data and control information for sending and receiving data).
  • B channel (64Kbps), D channel (16Kbps).
  • Codes analog voice into digital signals (PCM encoding).
  • Maximum of 8 bus terminals.

ADSL (Asymmetric Digital Subscriber Line)

An internet connection and data transfer system via a broadband telephone system. It uses the copper twisted pair subscriber loop installed in the RTB. ADSL2+ allows for higher transfer rates.

Characteristics

  • Maximum length: 5.5 km.
  • Maximum download speed: 8Mbps up to 2km of the subscriber loop.
  • Bandwidth: 1.1 MHz.
  • Asymmetrical because the data transfer speed is greater downstream to the user.
  • Splitter: Separates voice and data.

GSM (Global System for Mobile Communications)

A European mobile telephone system that defines all the characteristics, types of signals used, and the allocation of frequencies in the spectrum.

GPRS (General Packet Radio Service)

Data transmission technology that provides internet access through mobile telephones.

PCM (Pulse Code Modulation)

Modulation by pulses of a coded voice signal. Encodes by taking 8000 samples per second, each with 8 bits (64Kbps transfer rate).