Expected Speed

[mutant]

What is the fastest connection speed that can be expected when two modems communicate via analog circuits through a common central office? Assume good 56k modems and short circuit lengths.

The issue is that when we dial from both of these circuits to digital connections, we can get about 50k vs. 33.6 when connecting the two analogs circuits together.

I was hoping to see high 30s or low 40s.

 

[jimbopalmer]

for a pre v.92 56k modem to get over 33.6, it HAS to be connected to a digital line, any two analog lines can only do 33.6k or lower.

I am not sure about the new v.92 I tried to remain child-like, all I acheived was childish.

 

[pansophic]

At issue is the number of analog-to-digital (A/D) conversions that a connection can withstand. In order to achieve rates higher than 33.6K, you can only have one A/D conversion. Two analog modems, even running through an analog line simulator, have an A/D conversion at each modem and are forced to connect at V.32 rates.

There is a V.8 information exchange during the 2100Hz tone that occurs before the modems attempt to train. In this exchage the two modems will identify whether they are digitally or analog attached to the network. If both are analog then they start negotiation at V.32. If one or both are digital, then they will start negotiation at V.90 or V.92.

It sounds as if you are getting an excellent connection under the circumstances.
pansophic

 

[mutant]

Thanks for the education everyone.