| A | B |
|---|
| B channel | 16Kbps |
| D channel | 64 Kbps |
| BRI | 2 B channels+1 D channel |
| DDR | required for router to place ISDN call |
| DTE | PC< terminal, or router |
| NT1 | connects four wires to two wires |
| NT2 | smart device; can perform switching and concentrating |
| PPP | WAN data link encapsulation |
| PRI | 23 B channels+1D channel |
| R reference point | connection between a non-ISDN compatible device and a TA |
| S reference point | points that connect into the NT2; enables calls into parts of the CPE |
| T reference point | electrically the same as S point; references the outbound connection from the NT2 to the NT1 |
| U reference point | connection between NT1 and the phone company |
| T1 | basic unit of digital service: 1.544Mbps |
| T3 | basic unit of digital service: 45 Mbps |
| TA | converts non-ISDN compatible devices (TE2) to the ISDN network |
| TE1 | device that already speaks ISDN |
| TE2 | non-ISDN compatible (needs a TA to connect to the network) |
| ISDN allows only this many types to be used at a time | Single Encapsulation Type |
| I protocol | can be used over entire network |
| E protocol | used with telephone standards |
