Tiêu đề Module 4 Part 1.pdf ✅

 Public Switched Telephone Network (PSTN) is the global telephone system that handles voice-oriented telephone calls, is most commonly used to connect people world wide.  The telephone network is made up of:  Central Offices – the switching offices that serve the local telephone customers.  Toll Switching Centers or Tandem Toll Centers are used to connect customers to the toll network through the central office.  Primary Toll Centers are used for intrastate toll calling and  Sectional Toll Centers are used for interstate calls within a region.  Regional Toll Centers are used for interregional toll calling.  The telephone network consists of the interconnection of these different types of networks. By - Assistant Professor Nirali Thacker
By - Assistant Professor Nirali Thacker