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Studijní materiály
test12
BAN2 - Angličtina pro bakaláře- mírně pokročilí 2
Zjednodušená ukázka:
Stáhnout celý tento materiálBrno University of Technology
Faculty of Electrical Engineering and Communication
Department of Languages
ENTRANCE EXAM Postgraduate Doctoral Study
TELEPHONE EXCHANGES AND ROUTING
The function of a telephone exchange exchange (switch) is to interconnect four-wire lines, so as to permit a call to be established correctly. If both the calling and the called subscriber are connected to the same exchange, it merely has to interconnect them. If the wanted subscriber is connected to some other exchange, the call from the calling subscriber m ust be routed correctly, so that it will reach the wanted number.
There have been basically three generations of exchanges. The first was the step-by-step, or Strowger type, which had an incredible number of relays that made interconnections step by step, i. e., after each digit was received. The second generation was the crossbar exchange, which had even more relays but miniaturized and arranged so that up to 20 connections were made simultaneously by the crossbar switch, after all the digits were receive d . The processor-controlled exchange represents the third generation. Here, all the interconnections are made by the exchange processor or computer, and as a result the space occupied is very much smaller. It is worth pointing out that a telephone (or tel e x) exchange is an incredibly complex piece of equipment, and a 2000-line crossbar exchange may occupy the whole floor of a rather large building. In countries such as the United States and Australia, there are very few Strowger exchanges left, processor- controlled axchange capacities have outstripped those of crossbar exchanges, and most of the latest exchanges are digital. If the originating and wanted subscribers are not connected to the same exchange, the orginating exchange must participate in the co rrect routing of the call. This is done by analyzing the called number and examining the paths available through and outside the exchange to route the call. The local exchange must establish the group of first-choice trunks to which the call is routed, an d which of these is free. If all are occupied, the call is routed to the second-choice trunks, and so on. If no trunks are available, the appropriate signal must be sent to the calling subscriber, in this case perhaps a „plant engaged“ tone. The same process is performed in each exchange in the hierarchy of exchanges, which is essentially local office--toll center--primary or regional center--international center, and then the same chain in reverse.
TELEPHONE EXCHANGES AND ROUTING
A. Telephony has many of its own terms which appe
Vloženo: 4.06.2009
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