Testing your phone line

If you fail to get good connect speeds (at least 40 kbps) and your location and TelCo switch meet the requirements we described earlier, you should determine the quality of your phone line so you can ask your phone company to fix the situation.

You will need to use a terminal program like HyperTerminal that is included in Windows or any of the many programs that are distributed with modems or available for download.

Since HyperTerminal comes with Windows, might as well use it for our test.


  1. Go to Start/Programs/Accessories/Communications/HyperTerminal
  2. In the window double click on hypertrm.exe
  3. When the program comes up, type in TEXT for the name, and 1234 for the phone number and hit Enter. You will now be in a blank terminal window.
  4. Type ATZ and hit Enter, it will respond with OK
  5. Type ATDT###-#### (Where ###-#### is the number to your ISP) and hit Enter.
  6. After the modem dials, it will reply with “Login”, type +++, it will respond OK
  7. Type AT&V1 and press Enter

You should see something like the following:

MAX TX 26400 BPS
MAX RX 50667 BPS
Line QUAL 023
Rx LVL 012
Max Rx State 67
Max TX State 67
EQM Sum 0089
Min Dist 0000
RBS Ptrn 04
Rate Drop 00
Dig Loss 3F07
Loc Rtrn Cnt FF
Rem Rtrn Cnt FF

If the Line QUAL is more than 25 it indicates the line is noisy. Repeat this test several times to get an average.

Note also in the above test the modem was sending data at 26,400 BPS, and receiving data at 50,667 BPS. A 56K modem is asynchronous meaning it is faster in one direction than in the other direction.

Under current regulations connection to the Public Service Telephone Network (PSTN) at speeds in excess of 53K is prohibited and modems are designed to not violate this rule. If you normally see faster speeds reported your modem is showing the port speed at which it communicates with your computer, rather than the connect speed at which it communicates with your ISP. This can often be corrected by adding a command to your modem string.

Go to Start/Settings/Control Panel/System/Device Manager and right-click on your modem and click on Properties, click on the Connection tab and then click on Advanced. In the advanced window is a box labeled Extra Settings, type W2 in that box and click OK. The W2 command will take precedence and should force your modem to report connect speed. (Rockwell based PCI modems use the command MR=2). Some commands can override the W2 command so if that does not fix the problem, try adding S95=0, or S95=1 to the init string.

Modem Strings

There are hundreds of modems on the market from dozens of manufacturers. Each modem has an initialization string stored in it by the manufacturer that tells it how to function. Even though the AT command set is standardized, the combination of commands used in a particular modem may be very different than that in another model even from the same manufacturer. All command strings must begin with “AT” and end with “^M”. They can be either upper or lower case, but not mixed, and they are limited to a maximum of 39 characters not including spaces.

There is a “Basic Command Set” and an “Extended Command Set”. Extended set commands are preceded by an ampersand (&). The command ATZ means to use the modem default command string. A more specific command is AT&F1 which means to use the modem manufacturers command string, or AT&F0 which means to use the chipset manufacturers command string. The latter are extended commands.

The possible combinations of commands number in the thousands. An init string for one model of modem can thoroughly mess up some other model by causing command conflicts. Fortunately you don’t have to know anything about init strings because your modem and its manufacturer know. There are many tweaks that can modify how a modem handles certain functions. You can make it dial faster, connect only at a certain speed, change the speaker volume, and much more. All of this is mainly of little benefit for most users, and can create unforeseen problems. Only modify your manufacturers settings if you really know what you are doing, or on the advice of someone knowledgeable.


– Shelly –

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