2.3.3 Tx Connections

2.3.3 Tx Connections
A T1 line is a dedicated line that operates across 24 channels at 1.544Mbps. The European counterpart to this is E1, which uses 32 channels and can run at 2.048Mbps. A T2 connection (rarely used) adds more channels (96) and can operate at 6.312Mbps. A T3 line (E3 being the European equivalent) is a dedicated line of 672 channels able to run at speeds of 43Mbps. A T4 line jumps to 4,032 channels and speeds of over 274Mbps. Of the dedicated-phone-line options, T1 and T3 are the most commonly implemented.

Very few private networks require the capacity of a T3 line, and many do not even need the full capacity of a T1. The channels of a T1 or T3 line thus can be subdivided or combined for fractional or multiple levels of service. For instance, one channel of a T1 line's 24-channel bandwidth can transmit at 64Kbps. This single-channel service is called DS-0. DS-1 service is a full T1 line. DS-1C is two T1 lines, DS-2 is four T1 lines, and DS-3 is a full T3 line (equivalent to 28 T1 lines).