Autocall allows multiple users to contend for a limited number of resources within the network, reducing costs. As shown in the following illustration, a headquarters office in Los Angeles is connected over three separate WAN links to field offices in Chicago, Simi, and Dallas. Each office is served by a Passport 4400 unit equipped with a T1 Voice Module and a Digital Voice Module, and connected to the trunk side of a local digital PBX. The trunk access number at each PBX is 80.
Each Digital Voice Module is assigned a 3-digit Passport 4400 network extension number as shown. In addition, the three field offices are provisioned with autocall enabled to extension number X345.
Any of the field office users can access the Los Angeles PBX by lifting the station telephone off-hook, dial access code 80, and be automatically connected to the Los Angeles PBX trunk. From there the user can dial any PBX station or dial an access code for a PSTN dial tone.
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