Path: utzoo!attcan!telly!lethe!yunexus!xrtll!silver From: silver@xrtll.uucp (Hi Ho Silver) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: Differences between HST and V42 Keywords: Modem, 9600bps, HST, V4.2 Message-ID: <1990Nov26.031104.8597@xrtll.uucp> Date: 26 Nov 90 03:11:04 GMT References: <11623@milton.u.washington.edu> Reply-To: silver@xrtll.UUCP (Hi Ho Silver) Organization: Not around here, pal! Lines: 91 In article <11623@milton.u.washington.edu> tsai@milton.u.washington.edu (Men-Shen Tsai) writes: $I am concerning buying a new modem to replace my old one. I reviewed the $Computer Shopper and found out there are different kinds of 9600 bps $modems. Several terms I don't really understand. Can some one in the $net help me to figure out the meaning of these terms? If there's a FAQ here, these should be in it (and if they are, they should be read ...) $1. What does HST mean, and what are the differences between HST and $ V4.2? HST (High Speed Transfer ... or is it Transmission?) is USRobotics' proprietary modulation scheme to achieve higher-than-2400 bps throughput. It goes up to 14.4 kbps, and was devised back in the days when there wasn't even a 9600 bps international standard. If you buy the USR HST modem, you'll be able to communicate at 14.4 kpbs with another USR HST modem, but only at 2400 bps with other manufacturers' modems. Also, this is an asymmetrical protocol - while there is a channel in one direction running at 14.4 kbps, the return channel runs only at 450 bps. For many users, this is not a problem (downloads from a BBS or remote control of a PC, for example, are largely one-way transfers). However, if you're using it to do UUCP between Unix boxes, you'll get terrible throughput since the 450 bps channel won't satisfy the protocol. As for V4.2, there's no such thing. Perhaps you mean V.32, which is the CCITT international standard (heh) for 9600 bps modems. Perhaps you mean V.42, which is the CCITT international standard for error correction (this standard includes LAP-M and MNP level 4). BTW, the reason I said (heh) beside V.32 is that if you happen to buy V.32 modems from different suppliers, they may or may not work with each other. For more info on this, read the latest PC Magazine. $2. Some modems are able to transmite in the speed of 19.2K if it is $ in COMPRESS mode. What does the COMPRESS mode do when I transfer $ files? Well, as one would probably expect, it compresses them. Or, to be more precise, it attempts to compress them. MNP level 5, for example, will compress text quite well, executables fairly poorly, and may actually provide worse throughput when transferring pre-compressed files such as .ZIP archives. V.42bis, which is CCITT's standard for data compression, provides significantly greater compression on most files than does MNP 5, and it will simply allow pre-compressed files to flow through unhindered. With MNP 5, you can sometimes double your throughput, although you'll rarely get this much. V.42bis works better; it's supposed to theoretically compress by up to a factor of four, though 2-3 would be more realistic for most applications. $3. Is there any standard amoung these high speed modems? Is there any $ compatiable problems between modems? Yes, and yes. See above. $4. US Robotics modem has two different models, HST 9600 and Dual standard $ 9600. The price difference between these two models is about $300.0. $ What does DUAL STANDARD mean here? Actually, USR has three modems. They have a V.32 modem which uses the standard V.32 modulation techniques to achieve 9600 bps communications. They have an HST modem which uses their proprietary HST modulation to achieve 14.4kbps communications. They also have a Dual Standard modem which will use either. You are apparently considering USR (really? :-) Many BBSs use HST modems, so you will be able to enjoy very high throughput with such BBSs (check with the sysops before purchasing, if at all possible, to find out if your favourite BBSs are HST-equipped). Keep in mind, though, that the HST-only modem will connect with non-HST modems at a maximum speed of 2400 bps. That's the reason why USR sells a Dual Standard modem - it will allow 9600 bps connections with V.32 modems (assuming, of course, that the two modems happen to get along ...) As far as quality goes, USR has an excellent reputation. Two other things to keep in mind if buying USR (or, for that matter, with many other manufacturers) have to do with the various CCITT standards. Many manufacturers have recently added V.42bis data compression (and, a few months ago, V.42 error correction) to their modems. Make sure you get the most recent model, or else you might not be getting these protocols. Also, the V.32bis standard for 14.4kbps communications will be out next year; at that time, you can once again expect many manufacturers to scramble and introduce V.32bis modems. Should you wait? It depends on your present communications needs and equipment, and your future communications needs. Keep that in mind when buying. -- __ __ _ | ...!nexus.yorku.edu!xrtll!silver | always (__ | | | | |_ |_) |----------------------------------| searching __) | |_ \/ |__ | \ | if you don't like my posts, type | for ______________________| find / -print|xargs cat|compress | SNTF