Connecting 9600 and Beyond Free advice, and "For what it's worth" department: By Chip Morrow I have been asked about 9600 BPS and beyond more times than I care to think about, so the time has come to sit down and write a bit on this subject. If you are the least bit interested in upgrading to 9600 or 14400+ BPS, you might find this interesting. The only way to talk about this is via a history lesson of 9600 BPS as I see it. Just some observations: Many moons ago, the CCITT v.32 standard was not in use by anybody, as it was deemed to be too expensive to realistically build hardware to support the as-yet-unused international standard. Modem manufacturers retaliated by building their own proprietery 9600 connection schemes, and the next thing you knew there were modems all over the place that wouldn't talk to any other brand at 9600 and beyond. (If you bought a CompuCom 9600, you had to find another CompuCom 9600 to connect to if you wanted 9600 BPS operation. Etc. etc...) As connect speeds increased, so did errors in data transmission. Anyone who has ever used a "standard" modem of the 1200 or 2400 BPS variety can verify that you do occasionally experience line noise, which shows up as a burst of incomprehensible characters on your terminal. A 2400 BPS modem does not use NEARLY the bandwidth that high-speed modems do, so you can imagine what happens with one of these when you experience line errors. That's why "error correction" and "data compression" are built into the hardware on most of these things. We'll talk about THOSE in a bit here. Before all settled down, the one that rose to the top of the heap in the BBS world was USRobotics, with their proprietery HST modulation scheme, which is still in use on MANY bulletin boards today, including 1 node here. USR is still widely accepted in the BBS community as the leading manufacturer for BBS-compatible modems, but there is a price to pay (more on this in a minute). USR has since upped their proprietery HST protocol to 14,400 bps, and most recently 16,800. Problem is, you NEED a USRobotics modem to talk to them at that speed. USR does manufacture the "ultimate BBS modem" from my viewpoint, and that is the USRobotics Courier HST Dual Standard, supporting both their HST line, as well as the CCITT v.32 and v.32bis standards. With one of these modems, you can connect to virtually any bulletin board in the country at 9600 and beyond. Perfection has a price, however. The new Dual Standards are retailing for over $1,000 apiece (although they can be had for $700 or so thru direct channels). A little pricey from my standpoint. Which brings us back to v.32 and v.32bis. These are the accepted international standards for high-speed modems, and they are only just recently becoming widespread, and supported by MANY modem manufacturers. Virtually every modem manufacturer EXCEPT USRobotics has devoted their high-speed lines to the CCITT v.32 and v.32bis modulation schemes. Now, back to error correction and data compression. You're likely to have heard terms like MNP levels 1-5, v.42, and v.42bis. Strangely enough, NOT ALL HIGH-SPEED MODEMS SUPPORT THESE. I have seen some low-end v.32 modems that will connect at 9600 BPS, but with no error correction, meaning that your high-speed connections will be unreliable at best. Let's talk about these terms for a bit: MNP = Microcom Networking Protocol. There didn't used to be any standard for error correction/compression, and Microcom's imple- mentation gained wide acceptance pretty quickly. Most modems that support error correction support MNP. There are several "levels" of MNP built into many modems, even more than I'm going to bring up here, but here's what a few of the more common methods mean (briefly): Levels 1 through 4 = Error correction. The modems negotiate to the highest-supported level on both ends, and errors in transmission are "filtered" before they get to the remote terminal. Level 5 = Data compression. If "compression" is turned on on BOTH ENDS of the connection, and both modems support MNP-5, the modems will negotiate to this type of connection. Theoretically, this can increase throughput on file transfers. But, in reality, 90% of the files you transfer are already compressed (ZIP, ARJ, LZH, etc.), so the overhead of this protocol will actually slow you down. V.42 = Here comes the accepted international standard for error correction. It is generally felt that v42 hookups connect quicker and more efficiently than their MNP-4 equivalents. Most modems supporting V42 will "fall back" to MNP-4 if a v42 connection couldn't be made, and to no error correction if both fail. V.42bis = ...and here's the international standard for data compression. It is generally felt that v.42bis performs better than MNP-5, especially on noisy lines. Most modems supporting v.42bis will "fall back" to MNP-5 if a v42.bis connection couldn't be made. v.42bis is more efficient than MNP-5, and you will usually see higher throughput than with MNP-5. However, this method can STILL actually slow you down when transferring compressed files. Things to remember:  You're always limited by the phone lines in your area. If you get static on the line when you make a voice call, you can amplify that several times over when you make a high-speed connection. 9600+ uses just about all of the available bandwidth.  ERROR CORRECTION is a must. DATA COMPRESSION really isn't, although one tends to come with the other on most modems these days, and there are quite a few people who will tell you that you NEED v.42bis. I have always seen the best transfer speeds with error correction on, and data compression off. The one exception is if you transfer a lot of text and/or data files that are NOT already compressed. In that case, data compression really can speed up your transfers considerably.  Most any 9600 BPS modem (including the HST) will connect with any other high-speed modem at 2400 and below.  USRobotics' HST, like any other modem using a proprietery scheme, will connect 9600 and beyond only to another USRobotics HST modem.  USRobotics' HST Dual Standard (the pricey one) will connect 9600 and beyond with both their own HST's, as well as v.32 and v.32bis modems (which is just about the whole high-speed market). This works the other way, too, of course.  Any modem supporting v.32 should connect 9600 to any other modem supporting v.32 (from various manufacturers).  Any modem supporting v.32bis should connect 14400 with any other modem supporting v.32bis, as well as 9600 with v.32 modems. My advice: Stay away from oddball 9600 modems that won't talk to anything but other modems from the same manufacturer. USR's HST has a strong foothold in the BBS market, but that foothold is dwindling. v.32 and v.32bis are increasingly becoming the way of high-speed for the future. Go 14,400 BPS v.32bis, but be careful. Real-world pricing for low-end v.32bis has dipped under $300 apiece (closer to $200 on some internal models) from several different manufacturers (Zoom and Boca, to name but a couple). If you have a large wallet, get a USRobotics HST Dual Standard (*NOT* the cheaper HST model). They are very good, reliable modems, and most communications & BBS software have setup info for them. They were simply too expensive to be a practical option on this end. Make sure your system can handle the speed before you buy. You should have at LEAST a 10mhz machine (preferably a 286 or better), and at least a 16450 UART on your serial port, or you're likley to start dropping characters. If you're in a multi-tasking environment, or you find yourself dropping characters, you'll need a 16550 UART (which has a small built-in buffer to help out with this problem). Insist on error correction of some type, either MNP-4 or v.42. Otherwise, the line noise is likely to make life miserable for you. You'll likely also receive data compression with your modem, since one tends to come with the other. If you aren't transferring text files, turn off data throughput on compressed files like .ZIP, .ARJ, etc. There are people who will tell you that you'll do BETTER with v.42bis enabled, but that hasn't been the case in my experience thus far. BE WARY OF USED v.32bis MODEMS FOR A WHILE. Rockwell put out a bad set of the v.32bis chipsets a while back, and modem manufacturers are putting out updated ROMs for these modems at a bizare rate. You want to be able to return the modem if it's broken.