Overview of Virtual Tie Lines 87A site code can be any number of digits, but typically, one- or two-digitnumbers make the most sense. The dial plan at each site must includeappropriate routing instructions for each of the possible site code.Figure 11 shows three sites connected by VTLs. All sites use the samerange of extension numbers (1000 through 3999). To reach someone onanother NBX system, a user must dial a site code (61, 62, or 63 in thisexample) followed by an extension.Figure 11 Virtual Tie Lines Using Site CodesTo call someone in Atlanta, a user in Chicago must dial the site code 62and then the appropriate extension (1000 through 3999). To reach a userin Dallas, a user in Chicago must dial 63 and then the appropriateextension (1000 through 3999). Because the extension is preceded by thesite code, there is no conflict between the extension dialed and anidentical extension number at the local site (Chicago). The choice of sitecodes is made by the person who configures the dial plans for the sites.See “Dial Plan Configuration” on page 90 for more information on howto set up VTLs in the dial plan.Conference CallsUsing VTLConnectionsUsers can set up conference calls over VTLs in much the same way thatthey set up conference calls with other users at their local site, or at a sitereachable by an external telephone line.WANChicagoNBX SystemExtensions1000 – 3999AtlantaNBX SystemExtensions1000 – 3999DallasNBX SystemExtensions1000–3999Site Code 61Site Code 63Site Code 62
