Figure 6-1: Elements of the Public Switched elephone Network(PSTN) 3. Transport Core 3. Switch 3. Trunk Line The Transport core connects end office switches and core switches Trunk lines connect switches 6-76-7 Figure 6-1: Elements of the Public Switched Telephone Network (PSTN) 3. Transport Core 3. Trunk Line 3. Switch The Transport Core connects end office switches and core switches. Trunk lines connect switches