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Microsoft® Lync® Server 2013 Unleashed Second Edition by Randy Wintle, Alex Lewis, David Ross, Tom Pacyk

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Private Branch Exchange

A Private Branch Exchange (PBX) is a device that organizations install in their environment which enables internal connectivity for phones or fax machines. PBXs were historically expensive to purchase or required long lease agreements, but were considered an investment that could be utilized for a period as long as 10 to 30 years.

The PBX on-premise allows for users within the organization to call each other without traversing the PSTN and incurring any charges. A PBX also usually has trunk lines that connect to the PSTN so that internal users can make and receive calls with other PSTN users outside of the office, as shown in Figure 17.2.

Figure 17.2. A Private Branch Exchange (PBX).

As telephony has evolved over the ...

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