ModemTest V1.3 FAQ
Last updated: 12/December/2005
Q. My License key does not seem to work.
Both the User Name and Registration Key must be correctly
entered before the software turns itself into the registered version.
See this step by step guide for help.
Q. My modem defaults to pulse dialing but I need touch
tone (DTMF) dialing for my phone line.
Add the letter T before the phone number in the configuration
window to force touch tone dialling. (The letter P forces
plus dialling)
Q. How do I know which serial port (COM port) to select
in the configuration window.
In the configuration window a list of COM ports is displayed. Those that
are marked as In Use are already being used by another device (e.g. your
mouse). Those COM ports that are marked as unavailable could not be detected
as being installed in your computer. Those that are marked as available
have the potential to have a modem attached. So if you are not sure which
one to select try each Available port in turn. External modems tend to
use serial ports 1 or 2. Internal or USB modems tend to use ports 3 or
4. There is no fixed rule however.
Q. What Port speed should I use.
A
modem has two interfaces. One for your computer and one for the telephone
network. The port speed is the speed at which your modem and PC communicate.
The connection speed, also known as line speed, is the speed at which
the modem connects to another modem across the telephone network. Both
speeds are measured in bits per second (bps). Most serial ports can reach
at least speeds of 115,200bps. This is much faster than the connection
to the telephone network, which is typically 33,000bps or 56,000bps. If
the modem is using compression then the effective bit rate can be higher
than this. To avoid problems of slow transmission you should always select
a port speed that is higher than the connection speed. Most PC don't support
port speeds of 128,000 or above, so 115,200 bps is usually a good choice.
If you try and select a speed which is not available you will get an error
like, "Unable to configure the serial port, The parameter is incorrect"
Q. I get the error, "Unable to detect modem on this COM port"
What's wrong.
Check the following.
1. The modem is turned on
2. The modem is connected to the computer
3. The correct serial (COM) port is selected. (see above)
4. The modem is not already in use by another application (e.g. your internet
connection, fax software)
Q. I have a problem getting a connection, maintaining a connection
or the connection is slow.
Check the following.
1. Call waiting is turned off. Call waiting tones can interfere with modem
communications.
2. Try to disconnect all other telephone devices (telephone handsets,
answering machines, faxes, cordless phones, etc..) connected to the same
phone line as the modem.
3. Temporally remove extra devices such as surge suppressors, splitters,
phone line extenders, etc… Plug the modem directly into the wall.
4. Check that the telephone cable is plugged into the LINE socket on the
modem and not the PHONE socket. Note that not all modems will have both
sockets in any case.
5. Check that no one else is using a phone that is connected to the same
line as the modem.
6. Check that the correct slave phone number is entered for the computer
configured as the Master.
7. Check that the slave has been started and is waiting to receive a call.
8. For modems that have firmware that can be reprogrammed, check with
the modems manufacturer that you have the latest version.
9. Check that the modem you are trying to connect to supports the same
standards. (There were until recently several different standards for
56Kbps modems, these were called, x2 and K56flex. These have now both
been superceded by V.90)
Q. My connection speed varies from one call to the next, why.
The connection speed of a modem is limited by the telephone network. The
telephone network was designed to carry the human voice and because of
this, there is fairly low limit on how much data can be pushed through
the network. Modems that use the V.34 standard (28.8Kbps & 33.6Kbps)
as well as the newer V.90 standard (56Kbps) are at the limits of what
the telephone network can handle. In general it is only under ideal conditions
on a high quality telephone network that the maximum transmission speeds
can be obtained.
When the slave modem answers there is a brief period of negotiation to
determine the maximum speed that can be supported. The same modem may
perform quite differently when used from a different location or when
it is used to call a different destination. Also, as this negotiation
period is fairly brief the speed negotiated can vary significantly from
one call to the next due to small differences in line quality.
Q. I have a 56Kbps modem but ModemTest never connects at this speed.
To use 56Kbps there must be only one analog to digital conversion between
your modem and the destination. You have no control over this as it is
dependent on your telephone company's infrastructure. In order to connect
at 56Kbps the destination modem must be connected with a digital line,
this might be a T1 line (E1 in Europe). Thus with ModemTest, which uses
two analog modems, with two analog phone lines 56Kbps will never be possible.
33.6kbps will be the normal maximum. However if your 56Kbps modem successfully
runs at 33.6Kbps with ModemTest, then higher speeds will be possible with
ISPs who have a direct digital connection. This is shown in the diagrams
below (for data transmitted from the left computer to the right computer).
There is however some other issues to be aware of. There were until recently several different standards for 56Kbps modems, these were called, x2 and K56flex, these have now both be superceded by V.90 and they don't all work together. Also, even with a 56Kbps modem in perfect conditions the connection is asymmetric. You can only get 56Kbps in one direction (downloads). For uploads you are limited to 33.6Kbps. By contrast, with lower connection speeds you get the same speed in both directions. Some PABX's (company switchboards) will also stop 56Kbps connections from being established.
Q. In local diagnostic mode, the transmit and receive speeds are lower
than they should be.
In this local diagnostic mode a data packet is sent to the modem, then
ModemTest pauses waiting for the modem to echo the packet back to the
PC. Because of this pause in transmission the full data rate will never
be achieved with the local test. This is not the case for the master /
slave test method where multiple software threads are used to transmit
and receive data as fast as the modem and PC will allow.
Also, in some modems a very low modulation rate is used for the diagnostic loopback mode. (sometimes as low as 0.3 or 1.2Kbits / second). This is hardcoded into the modem and can not be changed by the user.
Q. Can ISDN, ADSL or Cable modems be tested with ModemTest.
No. Only dial up modems are supported. In most cases it is not possible
to directly connect ADSL and Cable modems directly to each other. ISDN
may be a possibility for future versions of the software.
Q. Why isn't there a test option to directly connect two modems together
(with using the telephone exchange).
Not many modems are capable of being connected directly together. Most
assume that you have a telephone exchange in the middle. The exchange
provides a current loop, dial tone and ring tone.
Q. When running local diagnostics with Windows ME, I get error like,
" Missing data: 288 bytes expected. 116 bytes received". or
" ERROR, Packet is X% corrupt. Offset: X. Bytes Out: XXX, Bytes In:
XXX", Why ?
We have seen this problem with a few different internal PCI modems
(soft modems) from various different manufacturers. Investigation has
shown this to be a bug in the Microsoft Windows WDM driver when using
the VCOMM interface in Windows ME. This problem should not affect your
modem when connecting to your ISP however. The Microsoft driver seems
to ignore time-out settings. This problem only affects Windows ME and
ModemTest 1.2 build 1008 and above contains a workarond for this problem.
Q. I am using Windows95 or NT4 and ModemTest doesn't run. I see an
error about a missing file.
If you are running Windows95 or Windows NT4 you need to have Internet
Explorer version 4 or above installed. There are some Windows operating
system updates that are installed with Internet explorer that are required
for ModemTest. This is not required in later version of Windows.
Q. Can ModemTest be started from the command line.
Yes. Command line arguments are as follows
ModemTest.exe [/l] [/m] <COM port> <Log filename>
/l = Auto run in local test mode
/m = Auto run in master test mode
<COM port> = Modem COM port number to use (0 - 99)
<Log filename> = Test results file name (without a path)Example: ModemTest.exe /l 2 output.log
Q. In Master / Slave mode the master hangs up before a connection
can be established with the slave.
It might be because the Master timed out waiting for a connection. Try
increasing the time-out value in the configuration window.
Q. Where can I find more information about ITU-T V.56 modem complianence
testing.
See this page about using ModemTest
for ITU V.56 testing.