An Introduction to T-Carrier Hierarchy

T1 is a high speed digital network (1.544 mbps) developed by AT&T in 1957 and implemented in the early 1960's to support long-haul pulse-code modulation (PCM) voice transmission. The primary innovation of T1 was to introduce "digitized" voice and to create a network fully capable of digitally representing and transmitting voice information over, what was up until then, a fully analog telephone system.
Numerology: Note and please remember:  for T1 or DS1 we have
24-8 bit samples (8 x 24 = 192) plus 1 framing bit = 193 bits x 8,000 frames/sec. = 1.544 Mbps (not 1.536 Mbps)
 
(Source)
T-Carrier Hierarchy
  DS0*
64Kbps 
 1/24 T1 
1 Channel 
  DS1
1.544Mbps 
1 T1 
24 Channels 
  DS1C 
3.152 Mbps 
2 T1 
48 Channels 
  DS2
6.312 Mbps 
4 T1 
96 Channels 
  DS3
44.736 Mbps 
28 T1 
672 Channels 
  DS3C
89.472 Mbps 
56 T1 
1344 Channels 
  DS4
  274.176 Mbps 
168 T1 
  4032 Channels 

* DSn = "Digital Signal" n = "Tn data stream"


Another view (international) of hierarchy

An excellent reference:

All You Wanted to Know About T1 But Were Afraid to Ask: (local copy) an excellent summary of the low end of the "digital hierarchy."
 
 
 
This page was prepared and is maintained by R. Victor Jones
Comments to: jones@deas.harvard.edu.

Last updated May 5, 2004