(Digital Signal) A classification of digital circuits. The DS technically refers to the rate and format of the signal, while the T designation refers to the equipment providing the signals. In practice, "DS" and "T" are used synonymously; for example, DS1 and T1, DS3 and T3. See OC.

   NORTH AMERICA, JAPAN, KOREA, ETC.

            Voice
   Service  Channels   Speed
   DS0         1            64 Kbps
   DS1        24         1.544 Mbps  (T1)
   DS1C       48         3.152 Mbps  (T1C)
   DS2        96         6.312 Mbps  (T2)
   DS3       672        44.736 Mbps  (T3)
   DS4      4032       274.176 Mbps  (T4)


   EUROPE (ITU)

            Voice
   Service  Channels   Speed (Mbps)
   E1         30         2.048
   E2        120         8.448
   E3        480        34.368
   E4       1920       139.264
   E5       7680       565.148


   SONET CIRCUITS

   Service          Speed (Mbps)
   STS-1   OC1       51.84 (28 DS1s or 1 DS3)
   STS-3   OC3      155.52 (3 STS-1s)
   STS-3c  OC3c     155.52 (concatenated)
   STS-12  OC12     622.08 (12 STS-1s, 4 STS-3s)
   STS-12c OC12c    622.08 (12 STS-1s, 4 STS-3c's)
   STS-48  OC48    2488.32 (48 STS-1s, 16 STS-3s)