E1 and T1 voice functions
E1 and T1 mainly provide voice and signaling trunks to the PSTN. To realize this function, the router must have E1 and T1 voice interfaces and be configured with functions required for transmitting voice over E1 and T1 lines.
The E1 and T1 voice physical interfaces are VE1 and VT1 interfaces, respectively.
PSTN and routers are connected through E1/T1 trunks, as shown in Figure 17.
Figure 17: Network diagram
E1/T1 voice transmission allows a router to provide more channels of voice communication, greatly improving router utilization and broadening service range.