|July 2000||Internationaly accepted.||
|V.92||V.90 compatible. Modem on Hold (Where available). Quick Connect. upstream rate increase by 42%.|
X2 and K56Flex compatible. Only one A/D conversion point can be used.
Only one conversion point where an A/D conversion point appears. If more then one A/D conversion point is present, rates cannot achieve 56k.
Images courtesy of . See the . (snapshot courtesy of )
|Lucent, Rockwell||K56Flex||Lucent Win modems and Windows ME. Use
|3Com, U.S. Robotics||X2|
|V.42||No speed improvment over V.32 bis. Offers better error correction.|
Every A/D conversion adds noise. More noise means less data and speed. Prior to ISPs using digital lines and the V.90 advancement, 33.6K was the ceiling. Some phone networks still have legacy systems, and are still limited to these connection speeds at best.
|Sep 1994||ITU||28800||V.34||28.8K with auto fallback to 24K or 19.2K. Backwards compatible with V.32 and V.32 bis|
|V.FC||Interm modem standard. V. Fast Class. Rarley used or seen since V.34. Not compatible with rates in excess of 28.8 KBPS.|
|Feb 1991||ITU (CCITT) Study Group 17||14440||V.32 bis||V.32 compatible. Rapid Rate Renegotiation (allows fast resych on the fly). 12000 and 7200 BPS fall back.|
|1989||ITU||9600||V.32||4800 and 2400 BPS fall back. Data compression and Error correction can push connection speeds to 19.2 KBPS|
|1989||Microcom||MNP||Use of MNP becomes a de facto standard.|
|1984||Bell System split up. Increased competition begins.|
|1984||9600||Uses echo cancelation|
|1200||Bell 212||Uses PKS (Phase Key Shifting)|
First publicly available modem.
Uses FKS (Frequency Key Shifting)
Error Correction vs Speed
Error correction requires retransmission when an error is spotted. This allows it to replace the parts that were not received correctly. Retransmission slows data throughput, and can even choke out a connection. This is why faster isn't always better. Sure you can fix it fast, but if you have to fix it constantly, that's all you are doing. If you slow the rate, it's possible to have fewer errors. The less errors, the higher the throughput
Another note about speed from Lucent, a common modem manufacturer is (a text highlighted copy in Google's cache). Additional references below discuss the Lucent win-modem and common troubleshooting.