134 E1 AND T1 CONFIGURATIONIntroduction to E1 andT1This section covers these topics:■ “Overview” on page 2309■ “E1/T1 Voice Functions” on page 2309■ “E1/T1 Interface” on page 2310■ “Features of E1/T1” on page 2311Overview Plesiochronous digital hierarchy (PDH) system includes two major communicationssystems: ITU-T E1 system and ANSI T1 system. The E1 system is dominant inEurope and some non-Europe countries. The T1 system is dominant in USA,Canada and Japan.E1 and T1 use the same sampling frequency (8 kHz), PCM frame length (125 ms),bits per code (8 bits) and timeslot bit rate (64 kbps). They differ in these aspects:■ E1 adopts A law coding/decoding of 13-segment but T1 adopts m lawcoding/decoding of 15-segment.■ Each PCM primary frame of E1 contains 32 timeslots but T1’s contains 24timeslots. Each PCM primary frame of E1 contains 256 bits but T1’s contains193 bits. Therefore, E1 provides 2.048 Mbps bandwidth but T1 provides 1.544Mbps bandwidth.E1/T1 Voice Functions E1/T1 voice implements VoIP on E1/T1 line. To this end, your router must haveE1/T1 voice interfaces and be configured with functions required for transmittingvoice over E1/T1 lines.The physical interfaces carrying E1 and T1 voice interfaces are respectively VE1 andVT1 interfaces.When E1/TI is adopted for voice transmission, PSTN exchanges and routers areconnected by E1/T1 trunks, as shown in Figure 670.
