Principles of Synchronous Digital Hierarchy

279Synchronous Digital Hierarchy

PDH hierarchy. It is the equivalent or counterpart of E1 or European hierar-

chy based on ITU-T standards. Similar to E1, a T-1 also consists of 64-kbps

channels, but only 24 in number [as against 32 of an E1]. It is further multi-

plexed [4T-1s] to form a T-2, and T-2s are further multiplexed to form a T-3

[7T-2s]. The bit rate of a T-1 is 1.544 Mbps, that of a T-2 is 6.312 Mbps, and that

of a T-3 is 44.736 Mbps. T-1, T-2, and T-3 are also synonymously called DS1,

DS2, and DS3 for digital signal levels 1, 2, and 3, respectively.)

Its container is called C11, virtual container is called VC-11, and the tribu-

ta