Definition Network switching is the process of transmitting data packets from the source to the destination through a number of intermediate network nodes. Here, each node controls or switches data packets to the next node towards the destination. When data comes on a node it is called ingress, and when data goes out of a node it is called egress. Switching Methods The two broad level switching methods are connection oriented switching and connectionless switching. Connection – oriented Switching : In connection – oriented switching, a dedicated path is established between the source and the destination before data switching. ... Read More

Pulse code modulation (PCM) is a technique of digitally representing analog signals. It takes samples of the amplitude of the analog signal and changes it to binary data. PCM technique is used by codecs in telephone networks to convert analog signals in local loops to digital signals in the trunks, and reverse conversion at the receivers’ end. Operations in Pulse Code Modulation The operations in PCM technique involves operations at the transmitting end and the operations at the receiving end. Transmitting End − In the transmitting end, the analog signals are sampled, quantized and encoded. The codec samples the analog ... Read More

Analog Telephone Cores The early telephone networks had analog cores. Frequency division multiplexing (FDM) was used to transmit a number of voice signals over the single line. Twelve calls were multiplexed into a group. Five groups were multiplexed into a supergroup. Digital Telephone Cores The present telephone networks have digital cores. This requires that the analog signals in the local loops are converted to digital signals that are transmitted via the trunks. This is done by codec (coder decoder). Time division multiplexing (TDM) is used to multiplex digital signals in the trunks, since it can be entirely handled by digital ... Read More

Trunks Definition Trunks are a large-bandwidth communication channels connecting switching centres, forming the core of the telephone network. A trunk comprises of a cluster of broadcast frequencies that are suitable for long haul communication of many voice and data signals simultaneously. Features The characteristic features of a trunk are − They carry digital information as opposed to analog signals carried by local loops. They are designed for both voice and data transmission. They can carry millions of calls simultaneously over long distances. They have very high bandwidth. They generally comprise of a cluster of fiber optic cables bundled together ... Read More

DefinitionPassive Optical Network (PON) is a FTTH (Fiber to the Home) technology deployed in both domestic and commercial consumers. It is called a passive network since it does not require a power equipment to amplify or process signals. A PON implements point – to – multipoint architecture, where a single optical line is divided into many optical splitters to serve multiple customers. It is used in the last mile of the network connection between an ISP and a user.ArchitectureThe passive optical network has three parts −Optical Line Terminator (OLT) − This is the end office of the service provider.Optical Distribution ... Read More

Definition Fiber to the home (FTTH) is a technology to deploy optical fibers in the local loop of the telephone networks to the users’ home for providing high-speed data connectivity. It replaces the existing copper wires as telephone lines to the customer premises by optical fibers that allow much greater bandwidth and less noisy connectivity. FTTH Council The FTTH Council is a non-profit organization to provide advanced FTTH solutions. Its members comprise of manufacturers, organizations and municipalities who build and install equipments for FTTH systems. The purpose of the Council is to share knowledge and build industry consensus on FTTH. ... Read More

DefinitionDigital Subscriber Line (DSL) is a communication technology that offers high – bandwidth digital communication over standard telephone lines formed of copper wires.FeaturesDSL is a family of technologies under the general name of xDSL, for various x, like ADSL, HDSL, and RADSL. Originally, it was a part of the Integrated Services Digital Network (ISDN) and was called IDSL.DSL technology is used in the local loop of the telephone network, i.e. the part of the telephone network that connects the customer premises with the end office of the telephone company.Some DSL services provide more than the standard bandwidth of the telephone lines. ... Read More

Modem is an abbreviation of “modulator demodulator”. It is a network device that modulates digital information or bits into analog signals for transmission at the sending end, and demodulates the analog signals to bits at the receiving end. Telephone modems enables data communication between two computers over voice – grade telephone lines. Purpose and Usage The computers are digital devices that are connected via analog local loops of the telephone networks. So, there is a need to convert the bits to analog signals so that they can be transmitted via the physical channels; and conversely convert analog signals in the ... Read More

In a telephone system, the local loop is a two-wire connection between the subscriber’s house and the end office of the telephone company. It is commonly referred to as the “last mile” of the telephone network. The loop may run from 1km to as far as 10 km.CompositionTraditionally, local loops are composed of twisted pair copper cables. The old local loops have several limitations − narrow bandwidth, high attenuation, distortion of symbols, crosstalk's etc.In recent times, copper wires are being replaced by fiber optic cables for faster and more accurate performance. Installation of fiber cables is popularly known as FttH ... Read More

The telephone system model is organized as a highly redundant, multilevel hierarchy. It comprises of the following components −Telephone of the subscriber or end userEnd office − Local central office directly connected to end user at a distance of 1 – 10km.Local loop − A two-way connection between the telephone and the end office.Toll office − switching centres which are called tandem offices when located within the same local area.Toll connecting trunk − Lines that connect end offices with toll offices.Intermediate switching offices − Interconnected non-hierarchical switching offices for connecting toll offices.Inter toll trunk − Very high bandwidth channels that ... Read More