This book provides an introduction to the different types of private telephone systems, how they operate and common call processing features they offer. Private telephone systems are communication equipment and software that are owned, leased or operated by the companies that use these systems. Private telephone systems are converting from company unique (proprietary) circuit switched systems to industry standard packet data voice (IP Telephony) systems. You will learn the basics of IP Telephony voice over Internet protocol (VoIP) and why it is so important to private telephone systems. The fundamental parts of private telephone systems are described including telephone stations, local wiring, switching systems, and numbering plans are described and explained. The high growth market for private telephone systems and the key trends are covered providing you with an understanding of which system types are growing the fastest and how some systems are evolving to better compete in the industry. Covered are the different types of private telephone systems. You will discover how multiline key telephone systems (KTS) operate and why they are converting from mechanical systems to automated electronic controlled networks. You will learn how automatic switching systems are used by private branch exchange (PBX) systems to provide features and services not offered by public telephone companies. Explained are the ways private telephone systems can be operated (hosted) by other companies (Hosted PBX/Centrex) and how these systems can provide services similar to PBX telephone systems. Discover how telephone systems can be combined with company information systems using computer telephony integration (CTI). You will learn how IP PBX (iPBX) systems operate and why IPTX is the fastest growing area in private telephone systems. You will learn some of the ways private telephone systems are adding wireless capabilities and industry standard wireless private branch exchange (WPBX) systems. Important call processing features including distinctive ringing, call hold, call transfer, call pickup, line hunting and other features are described. Advanced private telephone system features are explained including automated attendant systems, automatic call distribution (ACD), Interactive voice response (IVR) and Voice mail (VM). A basic introduction to call centers is also included.