Many libraries are now connecting branches to their central site or their PCs to the Internet using T-1 or fractional T-1 circuits. First introduced by AT&T in the 1950s, a T-carrier line is the most common type of broadband communication line. A T-carrier point-to-point line consists of four copper wires: one pair to receive data, the other pair to transmit it. A T-1 carrier line offers a rate of 1.544 Mbps (million bits per second). A fractional T-1 is often available at 64, 128, 256, 512, and other levels below full T-1. What is less well known is that there are options above T-1.
T-1C, the equivalent of two T-1s, offers a bandwidth of 3.152 Mbps; T-2, the equivalent of two T-1Cs, offers a bandwidth of 6.312 Mbps; T-3, the equivalent of seven T-2s, offers a bandwidth of 44.736 Mbps; and T-4, the equivalent of six T-3s, offers a bandwidth of 274.176 Mbps. Library administers can expand bandwidth to whatever their facility needs. The only obstacle is cost. The monthly charge for T-1 service begins at about $400. A T-3 costs several thousand dollars per month.
