T1 = 24 – 64 kbps Channels

Each of the 24 DS0 (Digital Signal 0) channels are able to carry digitally encoded voice band telephone signals or data

All 24 channels combined form a DS1 with a 1.544 Mbps Transmission Rate

T2 = 96 – 64 kbps Channels

T3 = 672 – 64 kbps Channels

Developed by Bell Labs

Used in the United States and Japan

T1 – T3 Carrier System