PUBLIC TELEPHONE NETWORK

PUBLIC TELEPHONE NETWORK
 Communication must occur between distinct point but few organization can justify the cost required.
 LAN is characterized by high bandwidth and that company controls and maintain all the connectivity of devices as well as the transmission media (wire).
 The company could have transmission media like infrared or satellite communication to establish connectivity.
 Another possibility is different kind of cables can be used for connectivity
 A variety of commercial options are available that enable organization to pay per only the level of service they require.
It has two main types
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1. PSTN [PUBLIC SWITCHED TELEPHONE NETWORK]
 This commercial network has its own existing infra structure supplied by the Telephone Company or Cable Company.
 The feature of PSTN is its low speed, analog nature of transmission, a restricted bandwidth and also wide spread availability.
 It is designed for telephone network but if we want it for digital communication than modem is required.
 When the link setup is unreliable and can terminate without warning.
 At that time PSTN communication medium is advisable.
 This connects are easy to get at short notice. This is widely available and covers almost every location where people live and work.
 PSTN is mostly useful for occasional users or as a backup to the private services
 Fax machines can also operated in this network.
2. PSDN [PUBLIC SEITCHED DIGITAL(DATA) NETWORK]
 It covers number of technology available for public telephone network.
 The main feature is its high level of reliable and high quality of connection.
 They can support both low and high speed at appropriate cost.
 It can also use to link computer and system and network of one organization to several other organizations.