ATIS Telecom Glossary
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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.

 

 

 

 

 

 

 

 

 

 



 
These definitions were prepared by ATIS Committee PRQC
 
For more information on the work related to these definitions,
please visit the ATIS website and the ATIS Document Center