Cheap Modems: Pro et Contra
The speed of communication essentially depend on the firmware version. And the new version does not necessarily work on your old line more stable. Firmware often have to pick up for each line. Therefore, the possibility to choose among a large number of firmware is quite important for the successful modem settings.
Over the past year in the world of modems it was really only one significant event: the adoption in February 1998 protocol V.90. First there were two standard 56K connection: K56Flex, developed by a consortium of Lucent and Rockwell, and X2, promoted by US Robotics (now 3COM). Incompatible standards hurt everyone: users did not understand how to buy a modem providers suffered with a choice of routers.
V.90 was obtained by merging X2 and K56Flex, and it allowed to accumulate in the new standard best demonstrated these protocols, without giving preference to any of them. Supports V.90 can be installed in the vast majority of X2 and K56Flex-MOfleMOB. To do this, simply update their internal software. Moreover, you can upgrade to V.90 modems, some V.34 (33,600). It is important to know and the fact that many manufacturers have stopped producing models that do not support V.90.
V.90 and all-all-all
It seems that the V.34 (speeds of up to 33,600 bps) was the last full analog modem communication protocol. Connection V.34 assumes that both sides of the line of analog modems installed. However, many telephone companies have replaced outdated analog telephone stations to digital. That is, the telephone exchange associated with digital channels and analog lines are only stretched to the end users (so-called "last mile"). This station receives an analog signal (voice or modem signal) from the user, converts it into digital and transmits to the receiving station. That, in turn, converts the signal into "analogue" and transmits it to the recipient.
Distortions introduced in the analog-to-digital and digital-analog conversion, impose restrictions on the transfer rate. Therefore, 33,600 bits per second, the maximum speed of connection between two analog modems. However, most people use their modems to connect to the pooling providers are often connected to a telephone exchange digital channels. Therefore, data transmitted from the provider to the user is not subjected to analog-digital conversion (making the greatest distortion). This allows to increase the transmission rate to 56 kilobits per second. I stress that the V.90 (X2 as a K56Flex) — unbalanced protocol. That is 56 kilobits per second — the maximum data transfer rate from the provider to the user. In the opposite direction information is transmitted at a speed of 33,600 bits per second or less. Moreover, due to limitations on the power output pools providers speed V.90 (both 56K and other pro-tocols) bounded 53 kilobits per second. In other words, a 56K modem is theoretically capable of receiving data at a rate of 56 Kb / s, but to send them through communication lines are not allowed to fast 53 Kb / s.
There are other nuances 56K connection. Memory is insufficient for some modems simultaneous storage algorithms two protocols 56K. Therefore, the consumer has to choose between them. It all depends on which one is a 56K connection supported by your provider. If he has not had time to update their equipment to V.90, you should not rush to you. It is also useful to consider that most modems better support "home" 56K protocol, not V.90. For example, Modems 3COM (US Robotics) to work effectively with X2 than V.90. So it makes sense to take the time to upgrade if your ISP continues to support the older 56K protocols.
How We Tested
Testing was conducted using a phone line simulator SIM-3 firms "Analyst TC". We used three computers. One of them ran the simulator, has been connected to a second reference modem, and the third — the tested modem. The reference used by the modem US Robotics Courier. The choice due to its quality and objectivity of the highest prevalence (including modem pools and Internet service providers). All modems are initialized in accordance with the recommendations in the user. Perhaps, after a careful selection of modem initialization strings, some could show better results. However, we believe that few users will be engaged in this kind of experiments.
ATA command reference modem switches to full answer and to test the modem to command dial ATD. After connecting to the modem test be forwarded zip-file. Each experiment was carried out 13 times.
Modem connects the telephone line through the simulator SIM-3. Testing was conducted on three types of lines: "good". "average" and "bad".
Beneath "good" we mean line line with greater than -45 dB ratio "S / N", 21-29 dB attenuation frequency response and lack of progress, jitter and amplitude, pulse and other interference.
To "average" line allowed attenuation of 18 dB, the interference signal level floating in the range -44 dB — -38 dB impulse noise with a frequency of 18.8 Hz and a signal level floating in the range of -44 to -26 dB.
To "bad" line, we have increased the incidence of noise and impulse noise and set the damping response within 21-29 dB.
Unfortunately, our available equipment does not allow to test the performance of 56K protocols. All tests were performed at the connection protocol V.34.
"AWACS Jaguar 56 RE" $ 140
I confess that before I knew nothing about the company Avaks, nor about its products. A small Finnish company was founded in 1988 and entered the Russian market in 1996. The main occupation Avaks development of telecommunication systems. In Russia, the company offers a range of modems, adapted to our lines. For testing Game.EXE was granted modem "AWACS Jaguar 56 RE"Built on Rockwell RCVDL56ACF chipset and supports both K56Flex (proprietary protocol Rockwell), and V.90. In addition to the standard for the modern fax modem feature set and protocols, "Jaguar 56 RE" support technology and AudioSpan DSVD. Their essence is this: allow users to communicate with each other voice without breaking the connection. AudioSpan different from DSVD only by mixing voice and data. The first technology combines the channels into analog form, the second digital. Naturally, the use of each of them leads to a decrease in the data rate.
To use AudioSpan and DSVD need to establish a direct connection between the two modems simultaneously supports one of these protocols. Neither of which connect through the Internet we can not go. AT "User’s Guide "Jaguar 56 RE" (unfortunately only available in electronic format and in English) given initialization strings for each of the voice protocols. In order to communicate in parallel with the data transfer, just connect a microphone and speakers (headset) for both modems, correct them (modems) and initiate a connection. It’s all. You can talk. No additional software is needed. In principle, this is very convenient. Imagine being able to finish off an opponent in deathmatch’e and then sympathetically ask his health. The only pity is that the game can be only two.
It included a CD with modem communication package Cheyenne BitWare, running under Windows 95. The program produces a very good impression. With BitWare can send and receive faxes. In this incarnation product Cheyenne, of course, can not compete with WinFax Pro in the number of options and elaboration of the interface, but all the features it is equipped. I think that the opportunities for BitWare faxing enough vast majority of readers. Bitware also allows "Jaguar 56 RE" as an answering machine. Welcome, you can either record by connecting a microphone to the modem or import of wav-file. Also, included in BitWare simple terminal supporting nevertheless basic file transfer protocols (mainly Z-modem) and a telephone database.
When testing "Jaguar 56 RE" I was leading on all three types of lines. And the gap increased with the improvement of the quality of the line (7% on a bad line up to 32% on the right). Generally, under the same conditions on the line "Jaguar 56 RE"Usually connect at a higher speed than SupraExpress.
A few words about the possibilities of setting "Jaguar". The modem allows you to adjust the output level in the range of -15 to 0 dBm (the advice and assistance in carrying out the testing. Designation of the module is stored in the register S91). By default, the level is -10 dBm. Its increase (decrease in number S91) leads to an improvement in the ratio "S / N"That can help to noisy lines or lines with high attenuation. It is necessary, however, be borne in mind that an increase in the output level of the echo causes an increase (an undesirable effect). The optimum value of the output level depends on the line and can vary during the day.
Outcome "AWACS Jaguar 56 RE" — Quality and inexpensive modem for home. Pay attention to it, if the need voice functions or can not afford to Courier or U336-E. Also, do not forget about such an important thing as a seven-year warranty from the manufacturer!
SupraExpress 56E Pro $ 90
It is impossible not to note the low price 56E Pro. This testing was the most expensive of the modems Diamond. SupraExpress 56E Pro curious and clearly avant-garde design. I am not inclined to attach importance to the appearance of the periphery, but many users are not indifferent to the look of the box with lights, standing them on the table. 56E Pro, by the way, the smallest of the external modems have ever come across in our laboratory.
Unlike "Jaguar 56 RE" "Supra" does not support the protocol and AudioSpan DSVD. Functions of the voice, however, and it has a modem.
56E SupraExpress Pro can operate either with V.90, K56Flex either, but not both protocols simultaneously. The copy provided .EXE, was installed with firmware V.90. Customers needing K56Flex, can download the appropriate firmware with Web-site Diamond Multimedia.
In addition to the drivers for Windows 95/98 / NT comes with the modem communication package The CD contains XtreemMachine. Use it to send and receive faxes, turn 56E Pro is an answering machine and even arrange a small BBS. The modem will determine the type of call (fax / voice / modem) and give preference to the corresponding function. But, I confess, I was not engaged in long-term studies "software"Supplied with SupraExpress 56E Pro and "Jaguar 56 RE". At first glance, functionality and XtreemMachine BitWare very close and will satisfy most users.
Test results 56E Pro can not be called spectacular. The stability of the modem to lines of poor have no complaints, but the rate could be higher. The reasons for this behavior are unclear. It is not excluded that the problem arises from the insufficient level of the output signal. The value of register S91, sets the level of the output signal from the modem chips Rockwell, defaults to 13 (-13 dBm). The current version of the firmware allows 56E Pro is not written in the S91 value of less than 12. At "Jaguar" It had no such restrictions, and default S91 is 10 (-10 dBm).
Outcome. Inexpensive modem for home SupraExpress 56E Pro — a good choice for cash-strapped user.