Pstn structure pdf

Thus, COs traditionally had a serving area of three miles radius around them, about 27 square miles or 75 square kms. With suburban sprawl, we can't build COs every five miles, so in practice, new subdivisions are served from remote switches, which are low-capacity switches in small huts or underground controlled environment vaults.

The remote provides telephone service locally on the loops in the subdivision. The remote and the loops are connected back to the nearest CO via fiber or radio. Telephone switches are connected with trunks. While subscriber loops are dedicated access circuits, trunks are shared connections between COs. To establish a connection between one customer premise and another, the desired network address telephone number is signaled to the network to the CO switch or remote over the loop, then the switch seizes an unused trunk circuit going in the correct direction and the connects the loop to that trunk - for the duration of the call.

Unlike public switched telephone networks, there is no static connection between the two subscribers, instead data is dynamically routed over the data network using a virtual connection.

Since each data packet has a destination address, the packets can even be routed differently over the network. On the other end they are reassembled in the correct order and converted back into analogue speech.

The Voice over Internet Protocol, also called IP telephony, is a method of communication for making calls over a broadband Internet connection as an alternative to regular calls made…. In telecommunications technology, the abbreviation ISDN stands for the technical term "Integrated Services Digital Network" and refers to a digital standard for telephone networks. As the name…. The features of a PSTN are: Subscribers can be connected by entering telephone numbers The existing connections are primarily used to transmit speech information After hanging up the connection is closed and the resources used become available to other subscribers The term public switched telephone network is primarily used for public landlines.

The traditional structure of the Public Switched Telephone Network The traditional public switched telephone network has a strictly hierarchic architecture and a star structure. Huong Tuan. A short summary of this paper. This rings the phone. Time slots carry speech channels , respectively, and time slots carry speech channels , respectively. Time slot 16 is normally not used for speech, instead it is used as a bearer for signalling between exchange-control systems-mainly, the international standard signalling system 7 SS7.

If SS7 signalling needs to be carried this is placed in one of the time slots, typically TS24, which means that such PCM systems can support only 23 speech channels. DDFs may also be 2 8. A private numbering scheme is required to enable extension to extension dialling, also special codes e.