To operate in the switched mode, a voice channel must be configured with an extension number, and the Passport 4400 unit must be configured with its assigned Device Network Address (DNA). Once configured, any voice channel at any node can be connected to any other compatible voice channel at any node. To do that, the telephone or fax user simply dials the extension number of the intended channel. An example of a switched voice system is shown in the figure below. Here, a headquarters office in Los Angeles is linked up with its branch office at San Francisco. Note that, in this example, there are twice as many voice channels at the San Francisco office as there are in Los Angeles.
A more complex switched voice system is shown in the figure below. In this example, a headquarters office in Los Angeles is linked in a 3-node network with its branch offices at San Francisco and Chicago. There are two voice channels at Los Angeles, three at San Francisco, and four at Chicago for a network total of nine. Any voice channel in the network can be connected to any other compatible voice channel.
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