What is T1? T1 is a term for a digital carrier facility (A.K. A a leased line) most commonly used in the United States, Canada, and Japan, to transmit a DS-1 (Digital Signal) formatted digital signals at 1.544 megabits per second. Developed by AT&T in 1957 and implemented in the early 1960's to support long-haul pulse-code modulation (PCM) voice transmission. The primary innovation of T1 was to introduce "digitized" voice and to create a network fully capable of digitally representing what was up until then, a fully analog telephone system.

DSL (Digital Subscriber Line) is a technology for bringing high- bandwidth information to homes and small businesses over ordinary copper telephone lines. xDSL refers to different variations of DSL, such as ADSL or SDSL. Assuming your home or small business is close enough to a telephone company central office (CO) that offers DSL service, you may be able to receive data at rates up to 6.1 megabits/second. Typically, individual connections will provide from 1.544 Mbps to 512 Kbps downstream and about 128 Kbps upstream. A DSL line can carry both data and voice signals and the data part of the line is continuously connected. DSL is expected to replace ISDN in many areas and to compete with the cable modem both in price and performance.