- 2070 Chaitra · 2 marks
Digital hierarchy of T-carriers
Short answer
T-carriers are the North American digital TDM hierarchy. A voice DS‑0 channel is 64 kbps. They are multiplexed in stages: T1 (1.544 Mbps, 24 channels), T2 (6.312 Mbps, 96), T3 (44.736 Mbps, 672), T4 (274.176 Mbps, 4032). T1 frame rate: (24×8+1)×8000 = 1.544 Mbps with one framing bit.
Explain the digital hierarchy of T-carriers.
T-carriers are the North American digital TDM hierarchy. A voice channel is sampled 8000 times/s with 8 bits, giving a DS0 = 64 kbps channel, and these are time-multiplexed in stages:
| Line | Digital signal | Channels | Rate |
|---|---|---|---|
| T1 | DS-1 | 24 | 1.544 Mbps |
| T2 | DS-2 | 96 (4 × T1) | 6.312 Mbps |
| T3 | DS-3 | 672 (7 × T2) | 44.736 Mbps |
| T4 | DS-4 | 4032 (6 × T3) | 274.176 Mbps |
T1 rate = (24 × 8 + 1) × 8000 = 1.544 Mbps, where 1 bit per frame is for framing. Higher levels exceed a plain multiple because of extra synchronisation bits (bit stuffing).
✓ Answer checked by Claude Sonnet 5.5
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