APPENDIX A : Standards

V.21            Standard for modem communications at 300 bps. Modems made in
                the US or Canada follow the Bell 103 standard. However, the
                modem can be set to answer V.21 calls from overseas.
V.22            Standard for modem communications at 1200 bps, compatible
                with the Bell 212A standard observed in the US and Canada.
V.22 bis        Standard for modem communications at 2400 bps. The standard
                includes an automatic link negotiation fallback to 1200 bps
                and compatibility with Bell 212A/V.22 modems.
V.23            Standard for modem communications at 1200 bps with a 75 bps
                back channel.
V.24            Standards layed down by the CCITT for interfacing a digital 
                device to a PTT-supplied modem. V.24 is also used as an 
                interface standard for connecting a peripheral device, such 
                as a visual display unit or a printer, to a computer.
V.25            Standard for modem communications that specifies an answer
                tone different from the Bell answer tone used in the US and 
                Cananda.
V.32            Standard for modem communications at 9600 bps and 4800 bps. 
                V.32 modems fall back at 4800 bps when line quality is 
                impaired, and fall forward again to 9600 bps when line 
                quality improves.
V.32 bis        Standard that extends the V.32 connection range: 4800,7200,
                9600, 12K and 14.4K bps. V.32 bis modems fall back to the 
                next lower speed when line quality is impaired, and fall back
                further as necessary. They fall forward to the next higher
                speed when line quality improves.
V.34            28.800 CCITT standard
V.34+           31.200 & 33.600, currently only supported by US Robotics
                (V.EveryThing modems) under consideration by CCITT.
V.35            See V.24.
V.42            Standard for modem communications that defines a two-stage
                process of detection and negotiation for LAPM error control.
                V.42 also supports the MNP error control protocol.
V.42 bis        An extention of V.42 that defines a specific data compression 
                scheme for use with V.42 and MNP error control.
X.3             It describes the functions of an X.25 PAD and the parameters 
                used to control its operation.
X.21            Interface between DTE and DCE for synchronous operation on 
                on public data networks.
X.25            Interface between DTE and DCE for terminals operating in 
                packet mode on public data networks.
X.28            It defines the interactions between a terminal and an X.25 
                PAD.
X.29            It defines the interactions between a host and its associated 
                PAD.
X.75            ISDN, EuroStandard, 64000.
X.400           Message handling systems : System model and service elements.
X.401           Message handling systems : Basic service elements and 
                optional user facilities.
X.408           Message handling systems : Encoded information type 
                convertion rules.
X.409           Message handling systems : Presentation transfer syntax and 
                notation.
X.410           Message handling systems : Remote operations and reliable 
                transfer server.
X.411           Message handling systems : Message transfer layer.
X.420           Message handling systems : Interpersonal messaging user agent 
                layer.
X.430           Message handling systems : Access protocol for teletex 
                terminals.
X.500           The directory (OSI Directory Services).
