Modem Problems and Answers

My 56k modem never connects at 56k!
This is one of the most frequently asked question we get at ECS. The answer is not simple so bear with me. First let's dispel some misinformation. It is just not possible to achieve 56k on many phone circuits. This is not false modem advertising. 56k modems are designed to wring as much speed out of the actual real-world connection as possible, and 50k or higher speed is only possible on a near-perfect connection.

What are typical connect speeds for 56K modems?
Typically, 42-46K for K56flex and anywhere from 44-52K for x2 is good performance.

Is initial connect speed all it's cracked up to be?
Initial connect speed is a convenient benchmark, but it can be deceiving. V.34 and 56K modems can and do shift their speeds up and down during the course of the call to respond to changing line conditions. Some modems connect very aggressively at high speeds, but are then forced to lower their speed to a more stable level. Others may connect conservatively and upshift.

What can I do to make sure my connection is going the fastest possible speed?
Make sure that you and your Internet service provider use the same 56K protocols. 56K requires that both ends have 56K modems, and they both have to use the same kind of 56K technology (x2, K56flex, or V.90). Despite what you may have heard, V.90 is not the same as x2 or K56flex. It is a third and distinct 56K protocol. Your ISP will be able to tell you which protocol they use. Some Internet service providers have separate phone numbers for 56K. Make sure you're calling the right number.

If there is a telephone, answering machine, etc., plugged into the back of the modem, unplug it from the back of the modem. The modem is supposed to ignore devices plugged into it when it is online, but that is not always the case. Try disconnecting additional telephony devices (fax, phones, answering machines, alarm systems, etc.) from the phone line, even if they're in a different room. Also try running the phone line directly from the back of the modem to the wall, without passing through surge suppressers, splitters, phone line extenders, etc. This is a basic and useful step in modem troubleshooting.

Watch out for dial-in numbers that are being forwarded to a distant location. A local number does not necessarily mean a local call.

The fact that your modem can connect at 56K speeds to a long distance number is no guarantee that the same is true of local numbers, and vice versa. Long distance calls may be routed through telephone circuits which are significantly better or significantly worse than the local circuits used to connect to your ISP.

Office PBX systems generally create an extra A/D conversion which will slow down a connection. How do you know if you're on a PBX? If you have to dial a number (usually 9 in the U.S.) to dial an outside line, you're on a PBX. If your phone has its own extension, you're on a PBX. The solution in that case is to plug the modem into a direct outside line. The office fax machine is usually dialed into a direct outside line, so try that.

The phone lines outside of your building may have equipment that introduces extra A/D conversions which slow down connections. Nonintegrated SLCs (Subscriber Line Concentrators) are one source. If that's the case, there's little you can do except to call the phone company and complain. Before you get your hopes up, be aware that the phone company is generally not sympathetic, and only guarantees speeds of 9600 baud or so (the exact answer will vary from telco to telco). It is worth a shot, though, and some people have managed to get their phone company to reroute the lines.

Even if I don't connect at 56K, I'm guaranteed 33.6, right?
No. In fact, even if you and your ISP were using 33.6 modems, you still wouldn't be guaranteed 33.6 connects. Few people get 33.6 connects. A large number get 28800 or 31200 connects, but many people only connect at 26400, 24000, or even slower. The phone lines in some areas simply can't support higher speeds.


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Modified 04/19/2005