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02-Hirarki Sentral Telepon. AKATEL Sandhy Putra Jakarta 2010. Hirarki sentral. Sentral lokal Sentral Tundem Sentral Trunk/Toll Sentral Gerbang Internasional. Phone Call Process.
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02-Hirarki Sentral Telepon AKATEL Sandhy Putra Jakarta 2010
Hirarki sentral • Sentral lokal • Sentral Tundem • Sentral Trunk/Toll • Sentral Gerbang Internasional
Phone Call Process • Requested destinations for phone calls are indicated to the central office (CO) switch by dialing a series of numbers (pulse or tone dialing). When the phone call is placed it will be handled by PSTN in the following way:
I. The phone call first arrives to the central office via a local loop, it is then processed in this local central office (also called end office or Class 5 office). This office has a switch that does the following: • Processes incoming calls. • Determines the best path to the call destination. • Establishes circuit connection.
II. Intra-LATA calls (not local but still within the same LATA) are handled by the local carrier (RBOC) since they are technically considered as long-distance calls. • If the local CO does not have a direct trunk to the destination CO, the call will be routed through a Tandem Office. • Tandem office: establishes intra-LATA circuit and handles billing procedures for long distance calls.
III. Inter-LATA calls are turned over from local carries to long-distance carrier like AT&T, MCI, U.S.Sprint. So, in this case the central office (CO) will merely forward the placed call to the local switching office of the long-distance carrier (called POP office) (also known as Class 4 toll center) POP: Point-of-Presence in a specific LATA for a long-distance carrier.
IV. If a Class 4 center cannot find a direct link to the destination Class 4 center, then the call will be handed over to the next level of switching up in the hierarchy (to Class 3 primary center). The goal in switching here is to keep the call processing as low on the hierarchy as possible for the following reasons: • Quicker call establishment and handling. • Maximization of cost-effective use of the lowest and least expensive switching offices possible (i.e. trying to use the least expensive and less number of switching offices). • The higher in the hierarchy means more routing flexibility to larger areas and more cost will be paid.
V. Class 3 primary center will in its turn hand it over to Class 2 sectional centers if there is no direct trunk.
VI.And finally Class 2 will hand it over to Class 1 regional center.