56k modem wont connect at anything over 28k

[johningram]

Whenever a computer trys to get internet access using a dial up modem in our office building it only gets a connection of 28k when it should connect at 48k or something closer to 56k. I know thats not the actual speed of data transfers but it wont even CONNECT at anything over 28k. The same pc will work fine on another phone line outside of our office.
Whats wrong?

 

[jimbopalmer]

If there is a digital phone system in your building, that would prevent speeds over 33.6k

all of the "56k" speeds (v.90 or v.92) rely on there being just one analog to digital conversion in the phone line. Motels, Offices and other users of digital phone systems have more than one analog to digital conversion so they cannot do the "56k" speeds, so v.34bis (33.6k) or v.34 (28.8k) is as fast as they go.

As many as 40% of the phone lines in the US cannot do any speed over 33.6k

I tried to remain child-like, all I acheived was childish.

 

[JPCPB]

Greetings,

Check this website:

http://www.modemsite.com/56k/trouble.asp

The right-hand side has links to articles on 56k compatibility, connection troubleshooting, etc.

Assuming it's not the building...!

Kindest regards,

James

 

[johningram]

Well im not sure if its ourt buildings fault because the line were using is supposedly a direct line from the outside. In the office if we want to dial out we press 9 but this line we do not have to. You just answer it and it has a dial tone already. My boss says its not connected to our phone system at all.

 

[pansophic]

Your problem, in all likelihood, is that there is more than 1 Analog to Digital (A/D) conversion taking place on the telephone line that you have, or you are dialing in to an analog modem at the distant end.

V.90 and V.92 require that only 1 modem be attached to the PSTN with an analog interface. If both are analog attached, then negotiation will begin at 33.6K (V.34). Also, because of the dense population of the phase-shift constellation required to do V.90, there cannot be more than 1 A/D conversion. Quanitization error gets to be too high with the second A/D conversion, and the modems quickly step down to V.34 speeds.

If you are dialing in to an ISP that supports V.90, then the trouble is likely with your line. If you are dialing in to another computer, and it is analog attached to the network, your line may be fine, you just can't have two analog attached modems achieve those speeds.


pansophic

 

[johningram]

Any ideas on how to get a line fixed? Can you get that to happen?

 

[johningram]

So your saying that if me and my buddy wanted to call eachother through hyper-terminal or something then we couldnt get full 56k or 48 or whatever? But if one of us call an isp that supports v.90 then it will work fine?
Why cant 2 regular average v.90 modems connect at v.90 speeds?

 

[jimbopalmer]

No ISP is using v.90 (or any other 56k variation) modems on analog phone lines at their end.
Sometimes ISDN, sometimes T1 but not analog phone lines.

Your analog phone modem always connect to a digital line modem at an ISP. if their are any other changes between analog and digital enroute, then it cannot go over 33.6k, two analog modem lines cannot got over 33.6k either.

I tried to remain child-like, all I acheived was childish.

 

[johningram]

Ok im not completely sure i understand.
Are most common modems analog or digital? It sounds like your saying two regular store bought modems will not connect at full speed. Is this the case?
Only when one side has a special expensive digital modem will the full speed work? Is that what your saying?

 

[jimbopalmer]

Yes. Two store bought analog modems can do 33.6k as best case, 28.8k is more common.

http://www.56k.com/basics/basics.shtml

http://www.56k.com/cons/onead.shtml

http://www.56k.com/cons/digital.shtml

I tried to remain child-like, all I acheived was childish.