Digital Signal X is a series of digital transmission rates based on DS0. The North American T-carrier and European E-carrier systems (see below) use these.
| DSX | Bit rate | Number of DS0 multiplexed together with TDM |
Used for |
| DS0 | 64 Kbps | — | One telephone voice channel |
| DS1 | 1.544 Mbps | 24 | T1 |
| — | 2.048 Mbps | 32 | E1 |
| DS1C | 3.152 Mbps | 48 | — |
| DS2 | 6.312 Mbps | 96 | T2 |
| — | 8.448 Mbps | 128 | E2 |
| — | 34.368 Mbps | 512 | E3 |
| DS3 | 44.736 Mbps | 672 | T3 |
| — | 139.264 Mbps | 2048 | E4 |
| DS4/NA | 139.264 Mbps | 2176 | — |
| DS4 | 274.176 Mbps | 4032 | — |
| — | 565.148 Mbps | 8192 | E5 |
T-carrier system was introduced by Bell in the U.S. in the 1960's. It uses time-division multiplexing to interleave multiple pulse-code modulation signals on a shielded carrier in each direction. Twisted pair at lower speeds, coaxial cables or optical fibre at higher. E-carrier is similar, used in Europe. E-carrier can support higher data rates for a given bit rate as it uses all eight bits per channel for signal coding.
| Format | Data rate |
| T1 | 1.544 Mbps |
| E1 | 2.048 Mbps |
| T1C | 3.152 Mbps |
| T2 | 6.312 Mbps |
| E2 | 8.448 Mbps |
| E3 | 34.368 Mbps |
| T3 | 44.736 Mbps |
| T3D | 135 Mbps |
| E4 | 139.264 Mbps |
| E5 | 565.148 Mbps |
SONET (Synchronous Optical Network) is much faster — you're generally talking about Internet backbone links.
| Format | Data rate |
| OC-1 | 51.84 Mbps |
| OC-3 | 155.52 Mbps |
| OC-12 | 622.08 Mbps |
| OC-24 | 1.244 Gbps |
| OC-48 | 2.488 Gbps |
| OC-192 | 10 Gbps |
| OC-256 | 13.271 Gbps |
| OC-768 | 40 Gbps |
And there there's a grab-bag of other technologies:
| Format | Data rate |
| GSM mobile telephone | 9.6-14.4 kbps |
| POTS (Plain Old Telephone Service) | Up to 56 kbps |
| GPRS (General Packet Radio System) | 56-114 kbps |
| ISDN BRI | 64-128 kbps |
| IDSL | 128 kbps |
| Frame relay | 56 kbps — 1.544 Mbps |
| DSL | 512 kbps — 8 Mbps |
| SDSL, HDSL | 1.544 Mbps |
| ADSL | 16—784 kbps upstream, 1—9 Mbps downstream |
| VDSL | Up to 52 Mbps downstream (max distance 1000-4500 feet) |
| Cable modems | 512 kbps — 52 Mbps 10 Mbps or less to node |
| HSSI (High-Speed Serial Interface), up to 50 feet router-to-WAN connection | Up to 53 Mbps |
| FDDI (Fiber Distributed Data Interface), used for corporate/campus WANs | 100 Mbps |
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| © Bob Cromwell Jul 2008. Created with /bin/vi, hosted on OpenBSD with Apache. Root password available here | ||||