T-carrier
The generic designator for any of several digitally multiplexed telecommunications carrier systems.
Note 1: The designators for T-carrier in the North American digital hierarchy correspond to the designators for the digital signal (DS) level hierarchy. See the associated table below.
Note 2: T-carrier systems were originally designed to transmit digitized voice signals. Current applications also include digital data transmission.
Note 3: If an “F” precedes the “T”, a fiber optic cable system is indicated at the same rates.
Note 4: The table below lists the designators and rates for current T-Carrier systems.
Note 5: The North American and Japanese hierarchies are based on multiplexing 24 voice-frequency channels and multiples thereof, whereas the European hierarchy is based on multiplexing 30 voice-frequency channels and multiples thereof. See table below.
| T-Carrier Systems | North American | Japanese | European (CEPT) |
|---|---|---|---|
| Level zero (Channel data rate) | 64 kb/s (DS0) | 64 kb/s | 64 kb/s |
| First level | 1.544 Mb/s (DS1) (24 user channels) | 1.544Mb/s (24 user channels) | 2.048 Mb/s (30 user channels) |
| (Intermediate level, North American Hierarchy only) | 3.152 Mb/s (DS1C) (48 Ch.) | – | – |
| Second level | 6.312 Mb/s (DS2) (96 Ch.) | 6.312 Mb/s (96 Ch.), or 7.786 Mb/s (120 Ch.) | 8.448 Mb/s (120 Ch.) |
| Third level | 44.736 Mb/s (DS3) (672 Ch.) | 32.064 Mb/s (480 Ch.) | 34.368 Mb/s (480 Ch.) |
| Fourth level | 274.176 Mb/s (DS4) (4032 Ch.) | 97.728 Mb/s (1440 Ch.) | 139.268 Mb/s (1920 Ch.) |
| Fifth level | 400.352 Mb/s (5760 Ch.) | 565.148 Mb/s (7680 Ch.) | 565.148 Mb/s (7680 Ch.) |
Note 1: The DS designations are used in connection with the North American hierarchy only.Note 2: There are other data rates in use, e.g., military systems that operate at six and eight times the DS1 rate. At least one manufacturer has a commercial system that operates at 90 Mb/s, twice the DS3 rate. New systems, which take advantage of the high data rates offered by optical communications links, are also deployed or are under development.