These standards and recommendations are issued by the International Telecommunications
Union (ITU-T), formerly the International Telegraph and Telephone
Consultative Committee (CCITT), which is a specialist agency
of the United Nations.
There are four series of protocol and standard references
that are commonly encountered in the area of communications
covered by this document. These are
| I Series |
Standards referring to ISDN and related
topics |
| Q Series |
Standards relevant to European ISDN networks |
| V Series |
Recommendations covering data
transmission over telephone lines |
| X Series |
Recommendations covering the interfacing
of data transmission and terminal devices |
The following list is for reference.
| V Series |
| Number |
Areas Covered |
| V.21 |
300bps PSTN duplex modems |
| V.22 |
1.2Kbps PSTN / leased line duplex modems |
| V.22 bis |
2.4Kbps PSTN / leased line modems |
| V.23 |
600bps/1.2Kbps PSTN modems |
| V.24 |
DTE and DCE interchange circuits |
| V.25 bis |
PSTN automatic calling and answering equipment |
| V.26 |
2.4Kbps leased line modems |
| V.26 bis |
2.4/1.2Kbps PSTN half duplex modems |
| V.26 ter |
2.4/1.2Kbps PSTN full duplex modems |
| V.27 |
4.8Kbps leased line modems |
| V.27 bis |
4.8/2.4Kbps leased line modems |
| V.27 ter |
4.8/2.4Kbps PSTN modems |
| V.29 |
9.6Kbps leased line modems |
| V.32 |
9.6Kbps PSTN / leased line modems |
| V.32 bis |
14.4Kbps PSTN / leased line modems |
| V.34 |
28.8Kbps PSTN / leased line modems |
| V.42 |
Error control procedures |
| V.42 bis |
Data compression for error control (V.42) |
