jeff@drexel.UUCP (Jeff White) (07/12/88)
This is actually a two part article. Our old 1200 baud modems (2 of them) finally bit the dust on us, so we are in the market for two new modems (hopefully at least 2400 baud) to replace them. I would also like to get a set that are equipped with MNP, if possible. However, I worked on one MNP modem before (a Microcom 9624x, the ones that can do 9600 baud), and in normal (non-MNP) mode, and at any baud rate, they had an absolutely incredible amount of line noise. It was almost impossible to get through one line without an error (or a lot of them) of some kind. I'm certain it wasn't the phone line itself, as other modems were used on the line with no problems at all (and the modem was used on other phone lines were no problems previously existed). My simple theory was that since the MNP software/circuitry was supposed to virtually eliminate all errros, that the basic modem didn't have to be that great. I would like to get MNP, just for the sake of having it for those that do have similarly equipped modems, but for those who don't, I can't afford to have such poor connections in normal mode. So, my two questions are: 1. Are all MNP modes pretty inferior in performance and noise rejections when operating in non-MNP mode, or was the one modem I worked on just a bad example (a lemon)? 2. Any recommendations for 300/1200/2400 baud modems which are reasonably priced and have MNP (or, can be upgraded to it at a later date at a reasonable cost)? Any help or recommendations would be greatly appreciated. Jeff White Drexel University - ECE Dept. rutgers!bpa!drexel!jeff
berger@clio.las.uiuc.edu (07/15/88)
The NEC 2420/30 is available with or without MNP. I use some extensively
over long distance, calling a variety of modems, and they perform admirably.
I don't have the MNP option in any of mine, and have never felt a need for
it. The MNP version of the modem is otherwise identical, however, so
it might be just what you're looking for.
I think this modem carries a 5-year warranty.
Mike Berger
Department of Statistics
Science, Technology, and Society
University of Illinois
berger@clio.las.uiuc.edu
{ihnp4 | convex | pur-ee}!uiucuxc!clio!bergerdavidsen@steinmetz.ge.com (William E. Davidsen Jr) (07/15/88)
In article <636@drexel.UUCP> jeff@drexel.UUCP (Jeff White) writes: | 1. Are all MNP modes pretty inferior in performance and noise rejections when | operating in non-MNP mode, or was the one modem I worked on just a bad | example (a lemon)? No. I don't know if you have a bad brand or a bad example, but not all modems with MNP have noise problems. | 2. Any recommendations for 300/1200/2400 baud modems which are reasonably | priced and have MNP (or, can be upgraded to it at a later date at a | reasonable cost)? We have hundreds of MultiTech 224E guys. All have MNP, most class three, a few class five. We're still buying them, and have been very happy. There is a problem in calling a non-MNP modem if you don't turn off the "auto-MNP" feature. When the modems have established carrier and baudrate, the MNP (calling) modem will send a tone burst which means "would you like to play MNP with me?" If the system you're calling has a login sequence, such as UNIX (and most BBSs), this can mess up the login sequence or cause a false baudrate. The simple soultion to this is to run the line from the computer to the modem at a fixed speed, like 4800, and let the modem do the flow control. That's not always possible, I realize. MNP does more for interactive use than for file transfer (I'm going to hear about that one) because file transfer protocols will reject bad packets while you can't reject a stream of bad characters on a screen, or use a system when it's getting a bunch of noise characters. Hope this helps, I'm sure thatre will be other opinions. -- bill davidsen (wedu@ge-crd.arpa) {uunet | philabs | seismo}!steinmetz!crdos1!davidsen "Stupidity, like virtue, is its own reward" -me
ashok@softart.UUCP (Ashok C. Patel) (07/16/88)
> My simple theory was that since the MNP software/circuitry was supposed to > virtually eliminate all errros, that the basic modem didn't have to be that > great. I would like to get MNP, just for the sake of having it for those This is just part of the problem. Another part of the problem is that the price of a 2400 bps modem has dropped so much due to competition, that the modem guts themselves are sacrificed. Another problem is that 2400 bps modems are noisier than the 1200 bps modems because the Rx and Tx bands are much closer together. That doesn't mean that you can't build a modem that isn't noisy just that it is more expensive. I would recommend the AT&T 4024CEO modem. It has a very good modem circuit, MNP and a fairly good price to boot. Other modems that I have heard of that are good (but I know nothing about) is the Practical Peripherals modems. (This is heresay and I don't think that they have MNP yet). --------------------------------- Ashok C. Patel Softart Microsystems Inc.