Overview
Plesiochronous digital hierarchy (PDH) includes two major communications systems: ITU-T E1 system and ANSI T1 system. The E1 system is dominant in Europe. The T1 system is dominant in USA, Canada and Japan.
E1 and T1 use the same sampling frequency (8 kHz), PCM frame length (125 μs), bits per code word (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 μ law coding/decoding of 15-segment.
Each PCM primary frame of E1 contains 32 timeslots but that of T1 contains 24 timeslots. Each PCM primary frame of E1 contains 256 bits but that of T1 contains 193 bits. Therefore, E1 provides 2.048 Mbps bandwidth and T1 provides 1.544 Mbps bandwidth.