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.