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- CCITT Hierarchy Nomenclature
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- Quaternary center (highest ranking) Class 1 Office
- Tertiary center Class 2 Office
- Secondary Class 3 Office
- Primary Class 4 Office
- Local Class 5 Office
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- Over the last decade, more and moer of the telephone switching environments
- have been under the control of stored programs residing withing the realm
- of ESS. These switching systems are controlled by intricate software
- modules exactly as any other sophisticated computers. The reprogramming
- of these switching systems is relatively straightforward in light
- of the requirements of the intelligent functions expected from the network.
- For the circuit switching part of the facility, the existing #1ESS (introduced
- in 1965 to local switching and to toll switching in 1970) and #1AESS
- (introduced in 1976 to local switching) have hte basic switching capacity
- to switch and be programmed accordingly. However, the common channel signaling
- aspects need to be upgraded to accommodate the intelligent network functions,
- especially those of the ISDN. The flexible and highly programmable
- digital switches are key components in the distributed and intelligent networks.
- In Norht America, the advent of the more sophisticated ESS facility
- (#5ESS) was a major step in the realization of intelligent networks.
- Its modular hardware and software building blocks permit the capacity to
- customize these switching systems to perform
- the flexible and programmable functions with inherent mechanized intelligence.
- The more recently introduced #5ESS switch will meet the CCITT requirements
- for the (2B + D), (23B + D), and the (30B + D) rate interfaces.
- In Europe, the steady evolution of the switching systems
- (Ericsson, AXE10) for intelligent network functions has been well along
- its way since 1984. The modularity for customization and for CCITT
- signaling system No. 7, which facilitates the customer services integrated in the
- network functions, has been incorporated into the newer switching systems
- being built in Europe. These switches also provide for the (2B + D),
- (23B + D), and the (30B + D).
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