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Path: news.aimnet.com!news From: JNavas@NavasGrp.com (John Navas) Newsgroups: comp.dcom.modems Subject: The Navas 28800 Modem FAQ - 1/6 Date: Sun, 21 Apr 1996 17:27:03 GMT Organization: The Navas Group of Dublin, CA, USA Message-ID: <317a6fda.61954633@news.aimnet.com> NNTP-Posting-Host: dial-bp1-2.iway.aimnet.com X-Newsreader: Forte Free Agent 1.1/16.198 Navas 28800 Modem FAQ IWAY 500 Winner NAVAS 28800 MODEM FAQ [MODEM PICTURE] (Answers to Frequently Asked Questions) BREAKING NEWS Hayes emerges from Bankruptcy[1] and hires new CEO[2] [new 4/18/96] WinFax PRO 7.0 for Windows 95 makes TAPI a reality[3] [new 4/11/96] Quarterdeck acquires Datastorm (developer of Procomm)[4] [new 3/28/96] Hayes releases Windows 95 drivers for ESP board[5] Microsoft releases Unimodem V driver for Windows 95[6] Hilgraeve offers free upgrade for Windows 95 HyperTerminal[7] Penril introduces 33600 modem[8] Motorola introduces Premier 33.6[9] 33600 upgrade for certain USR Sportster 28800 models[10] USRobotics changes Sportster S-registers[11] AT&T bails out of consumer modems[12] Diamond Multimedia acquires Supra[13] FIFO problem still exists in SMC "multi-I/O" chips[14] ZyXEL[15] releases long-awaited V.34 modem (ISDN-upgradable Elite 2864[16]) Motorola Lifestyle and Power Class modems can damage your serial port.[17] Copyright 1995-1996 John Navas, All Rights Reserved. Updated: Thursday, April 18, 1996. Permission is granted to copy for private non-commercial use only. Posted as http://web.aimnet.com/~jnavas/modem/faq.html[18]. Copies of this document in either hypertext (HTML) or plain text format may be obtained by email from an "agora" server (e.g., agora@kamakura.mss.co.jp[19]) or from web-mail[20]. For information on agora, send an email message to an agora server with a body of "help"; for information on web-mail, send a blank email message to web-mail@ebay.com[21]. Please note: The author has no present connection with any modem company (other than as a customer), and does not endorse the products of any company. This information was compiled by the author and is provided as a public service. Neither the author nor any organization mentioned herein are responsible for any errors or omissions, or for any consequential problems that might result. USE AT YOUR OWN RISK. Please note: The author does not have the time to give individual technical support, so please do not email requests for assistance. Instead, post them on the Usenet newsgroup comp.dcom.modems[22]. Thank you. Email comments and suggestions to JNavas@NavasGrp.com[23] Button[24] [The Navas Group home page[25]] ___________________________________ CONTENTS Why don't I get 28800 bps speed on my connections?[26] What's the difference between V.FC and V.34? What's next?[27] What are split/asymmetric speeds?[28] What is Selective Reject (SREJ)?[29] Do I need a 16550 UART? What is a UART?[30] Where can I get a 16550 UART?[31] Why am I getting CRC errors (overruns)?[32] [updated 3/29/96] What's wrong with my dialup SLIP/PPP connection?[33] Any Trumpet Winsock tips?[34] Where can I get updated video drivers?[35] [updated 4/11/96] Where can I get updated disk/SCSI drivers?[36] [updated 4/9/96] Why 1024 bytes for the Windows COM buffer?[37] What is "retraining"?[38] What are "fall-back" and "fall-forward"?[39] How do I set a speed greater than 19200 bps in Windows?[40] What about third-party comm drivers for Windows?[41] How can I share a modem between data and WinFax?[42] How can I display the status of an internal modem under Windows?[43] Why does Windows lock up when I access my modem?[44] Why can't I get back on-line after I escape to command mode?[45] What are the best (data/fax) comm programs for Windows?[46] Why do I sometimes have problems connecting?[47] Why do I sometimes get abruptly disconnected?[48] Why do connections sometimes seem to run slower and slower?[49] What is Distinctive Ring?[50] [new 4/11/96] How can I use a single phone for fax/data/voice?[51] [new 4/11/96] What is Caller ID?[52] [new 4/11/96] How do I shut off Call Waiting?[53] [new 4/11/96] How do I keep my data/fax call from being interrupted?[54] [new 4/11/96] Does USR Adaptive Answer work with Procomm Plus for Windows?[55] Any other USRobotics tips?[56] Any other Windows 3.x tips?[57] What are "voice" modems?[58] What is ISDN?[59] [updated 4/9/96] What are "cable modems?"[60] [updated 3/29/96] What are ADSL, SDSL, and HDSL?[61] Any Windows 95 tips? What is TAPI? What is Plug and Play?[62] [updated 4/11/96] Any other sources of related information?[63] How can I connect my modem to a digital phone system?[64] What modem initialization string should I use?[65] Where can I get information on my Rockwell-based modem?[66] [updated 4/11/96] What about magazine reviews?[67] Which 28800 modem should I buy?[68] [updated 3/29/96] Where can I get a good deal on a modem?[69] Which modem companies have a full Internet presence? Archtek Telecom[70] Best Data[71] Boca Research[72] Cardinal Technologies[73] Creative Labs[74] Diamond Multimedia[75] Global Village[76] GVC (MaxTech)[77] Hayes (and PPI)[78] [updated 4/18/96] Intertex[79] Logicode (Quicktel)[80] [new 4/11/96] MaxTech (GVC)[81] Megahertz[82] Microcom[83] miro Computer Products[84] Motorola ISG[85] Multi-Tech[86] Penril[87] Supra[88] Telebit[89] USRobotics[90] [updated 4/1/96] Zoom[91] ZyXEL[92] [updated 4/18/96] ___________________________________ Why don't I get 28800 bps speed on my connections? If you are unable to get connections at 28800 with your V.FC/V.34 modem, here are the probable causes and what you may be able to do about them. If you consistently connect at 26400 or above, consider yourself fortunate -- it's simply not possible to go faster than that on many phone circuits. (This is not false modem advertising -- 28800 modems are designed to wring as much speed out of the actual real-world connection as possible, and 28800 speed is only possible on a near-perfect connection.) Even if you consistently connect at lower speeds (e.g., 24000 or even 21600), there may be little you can do, but you can at least try the following: Make sure that your serial port is locked at 38400 or higher (57600 recommended). This is usually set within your comm application, not the Windows Control Panel (see "How do I set a speed greater than 19200 bps in Windows?[93]"). Try connecting to known good 28800 numbers (e.g., Hayes at 800-"US-HAYES; Multi-Tech at 800/392-2432; USR at 708/982-5092). This will at least tell you whether the problem is at your end or the other end of the connection. (The USR number is particularly useful, because you can get an on-line reading of connection quality from a USR BBS command.) Watch out for dialin numbers that are being forwarded to a distant location. It's a "dirty little secret" that many BBS (bulletin board systems) and ISP (Internet service providers) use Call Forwarding to extend their local calling areas. (Where location A to location C is a toll call, and an intermediate location B is local to both A and C, Call Forwarding from B to C effectively makes A to C a local call.) Although this can work fairly well at lower speeds (e.g., 14400), the extra connection hop(s) can degrade the signal enough to limit higher speeds (even as compared to a direct long distance call). If possible, test for premises problems by disconnecting all your premises wiring (and equipment) from the incoming telco terminating block, and hooking your modem directly to it. If your connections are better, you have a premises problem that you may be able to isolate and fix. Premises problems (faulty wiring and/or equipment like cheap phones and fax machines) are a frequent cause of 28800 connection problems. If that doesn't help, listen carefully to the quality of your voice connections. Note that you must dial a known quiet number, since many otherwise good phone lines exhibit excessive noise until you actually connect. (Dialing a single digit is not enough.) After you connect, if you hear more than very faint hiss and/or hum, then you probably have a line problem. While a quiet line is important, there are other line problems that can reduce your speed: bandwidth (frequency response), distortion, etc. It is difficult to test for these problems without proper test equipment, but it's still a good idea to listen carefully for audible problems, particularly if you can find a number that will send you test tones. You may be able to get your phone company to improve the quality of your line. Since phone companies are often reluctant or even unwilling to work on data problems, it may help to report that you are also having fax problems. Or you can try asking for a data or fax "specialist." Ideally you want the service technician to bring the right kind of test equipment, a sophisticated line or transmission test set, not just the normal basic tester. It may also help to ask for a BERT (bit error rate tester) or "data test set." Sometimes switching to a different cable pair from the CO (central office) will help. In extreme cases the author has resorted to ordering a new line, making sure that it is good when installed, and then canceling the old line. You may be told that you need a special "data" line, more properly called a "conditioned" circuit, which is considerably more expensive than a standard "voice-grade" circuit. Don't waste your money. All you need is a good quality "voice-grade" circuit. A final note: Add-on noise filters will not help -- they are the modem equivalent of snake oil. Your 28800 modem already has all the filtering it can use. An add-on filter will do nothing at best, and it may well make things worse. Button[94] [Return to top[95]] ___________________________________ What's the difference between V.FC and V.34? What's next? V.FC A proprietary specification for speeds up to 28800 bps, based on an early draft of the V.34 standard, that was rushed to market by modem chipset leader Rockwell International[96]. It works reasonably well, but lacks the sophistication and robustness of V.34; for example, V.FC does not support split speeds[97]. Many (but not all) V.FC modems are upgradable to V.34, but the modem typically has to be returned to the manufacturer for a "datapump" change. V.FC-only modems will not connect above 14400 bps to V.34 modems that lack V.FC support. With the advent of V.34, V.FC is rapidly fading as modems are upgraded. In the opinion of the author there is now little or no reason to get a modem that has V.FC but not V.34, although until V.FC fades completely there will still be a significant advantage to a modem that supports both V.34 and V.FC. V.34[98] A true international standard for speeds up to 28800 bps that is more sophisticated and robust than V.FC. Some (but not all) V.34 implementations support split speeds[99]. Extensions to V.34 for additional speeds up to 33600 (on extraordinarily good connections) have been drafted and are expected to be approved in 1996, although early products are already starting to appear from some companies (e.g., USRobotics[100]). V.34 is rapidly replacing V.FC in the marketplace. V.34-only modems will not connect above 14400 bps to V.FC-only modems. In the opinion of the author V.34 is clearly the modem standard of choice. It may well prove to be the last widely-supported analog modem standard. 28800-33600 fax Fax is currently limited to 14400 bps. Efforts are underway to define a 28800-33600 bps fax specification, which would probably be widely adopted. However, general availability is probably a few years away. Voice See "What are "voice" modems?[101]" Plug and Play[102] See "What is Plug and Play[103]" ISDN[104] See "What is ISDN?[105]" "Cable modems" See What are "cable modems?"[106] ADSL/SDSL/HDSL See "What are ADSL, SDSL, and HDSL?[107]" Universal Serial Bus A better way to connect a modem to your computer than the conventional UART or parallel port. (See "What is a UART?[108]") Expected to become a standard feature of many chipsets and motherboards (e.g., those manufactured by Intel) and operating systems (e.g., Windows 95), although USB is not yet available. (See "Universal Serial Bus Home Page[109]") See "Modems: the make-it-happen machines for the ultimately wired of the 90's[110]" Button[111] [Return to top[112]] ___________________________________ What are split/asymmetric speeds? In the past, most standard modems were only capable of transmitting and receiving at the same speed. (The exceptions were proprietary modems such as the USR HST that used greatly different transmit and receive speeds.) Since most connections were made at the maximum speed, there was little reason to support different transmit and receive speeds. With the advent of speeds up to 28800 bps that is no longer true. It's now quite common to have a connection where at least one (and often both) speeds must be limited to less than 28800 bps, and it's not uncommon to find that a connection will support faster speed in one direction than the other. (One reason is that send and receive channels are separated for transmission between telephone switching offices.) Having been designed to optimize performance over a wide variety of conditions, V.34 includes an optional specification for asymmetric (differing or split) transmit and receive speeds. For example, a connection might support a transmit speed of 28800 bps but a receive speed of only 26400 bps; without split speed, the speed in both directions would have to be limited to 26400 bps. For this reason split speed capability is a worthwhile and desirable feature. Not all V.34-compliant modems support split speeds. For example, at the time of this writing most "glue 'n go" Rockwell V.34 clones, do not support split speeds. On the other hand, others, including all USR V.34 modems (Sportster 28800/33600 as well as the Courier V.34), Supra, and Motorola, do support split speeds. Button[113] [Return to top[114]] ___________________________________ What is Selective Reject (SREJ)? Selective Reject (SREJ) is an optional, advanced LAPM (V.42) error correction capability that allows the receiving modem to request retransmission of a given block while continuing to receive later blocks; i.e., to receive the retransmission late (out of order). Without it, the entire transmission has to start over at the retransmitted block, which can result in later blocks being resent unnecessarily. Hence, Selective Reject can improve throughput where there is a significant error rate, particularly over links with long delays (e.g., satellite links). Not all modems support Selective Reject, which is typically found only in high-end products. Button[115] [Return to top[116]] ___________________________________ Do I need a 16550 UART? What is a UART? A UART (an acronym for Universal Asynchronous Receiver-Transmitter) is simply an interface chip. Your computer needs one to "talk" over a serial connection to serial devices such as serial printers and modems. Each serial device needs a UART chip to "talk" to your computer, even modems that are installed inside your computer. In computer terms the UART is very old technology. We continue to use them because we own so much software that depends on there being a specific kind of UART. Efforts to replace the UART and its particular serial architecture are ongoing (e.g., Universal Serial Bus[117]), but it's doubtful that the UART will be replaced anytime soon. There are many types of UART chips, but only two main types that are used in IBM-compatible personal computers: 8250/16450. Major weaknesses of the 8250 and 16450 are a lack of built-in flow control, and buffers that can only hold a single character. This means that the UART must be promptly serviced by the system processor each time a character is received, or that character will be wiped out by the following character, a condition called "overrun." (See "Why am I getting CRC errors (overruns) when downloading?[118]") 8250/8250A. The 8250 is the UART used in the original IBM PC. "Urban legends" notwithstanding, the 8250 and the improved 8250A are capable of speeds up to 115,200 bps. 16450. Slightly improved over the 8250, the main advantage of the 16450 is that it works better on computers with higher internal speeds. From a functional standpoint, however, it is essentially indistinguishable from the 8250, and suffers from the same weaknesses. 16550. A substantial advance over the 8250/16450, the 16550 has both a fully 8250-compatible mode and a newer mode that provides 16-character FIFO (an acronym for First In, First Out) buffers. When the old mode is enabled, it works just like an 8250; when the newer mode is enabled, the FIFO buffers greatly extend the time available for responding to incoming characters. The receive FIFO buffer has a variable threshold that can be set to values of 1, 4, 8, or 14 characters, with higher numbers giving less time to respond before the 16-character FIFO buffer is full; on the other hand, higher numbers can give slightly better performance, by allowing the system to process incoming characters in larger "chunks." A good rule of thumb is a threshold of 8 characters. (See "What about third-party comm drivers for Windows?[119]") Most (but not all) internal modems come with a 16550 UART. 16550. Certain versions of the original 16550 were buggy. It is best to avoid them. 16550A. Improved version of the 16550. Later types, the 16550AF and 16550AFN, are essentially indistinguishable, but even less likely to be buggy. These are the UARTs of choice. Look for the National Semiconductor[120] brand. 16552. Two improved 16550 UARTs in a single package. Clones. More recent designs typically package UART functionality (often two of them) in a single "multi-I/O" chip. Many of them work very well; however, some of them are buggy. (See "Why does Windows lock up when I try to access my modem?[121]") Some internal modems emulate UARTs with on-board logic rather than using actual UART chips; these products can provide more effective buffering than a conventional UART. More advanced UARTs (e.g., 32-character FIFO buffers, built-in flow control) are becoming available, but they are generally not needed. Parallel modem interfaces and the Hayes ESP card are alternatives to UARTs, but they require special drivers and provide no significant advantage over the 16550A in the opinion of the author. In general, a single-task operating system like MS-DOS can get by with an 8250/16450 UART with serial port speeds of 19200-57600 bps (depending on the speed of the system processor) and well-written software. This is usually adequate for even a 28800 bps modem. However, a multitasking operating system like Windows, OS/2, or UNIX, will usually need a 16550 UART. (Nevertheless, if you are stuck with an 8250/16450, you can probably still use a 28800 bps modem if you are careful.) You can tell what kind of UART chip you have by running Microsoft's MSD[122] (which comes with Windows), being sure to run it outside of Windows. (The reason is that Windows can hide the true state of the UART from MSD.) The Universal Serial Bus (USB) is a better way to connect a modem to your computer than the conventional UART or parallel port. USB is expected to become a standard feature of many chipsets and motherboards (e.g., those manufactured by Intel) and operating systems (e.g., Windows 95), although it is not yet available. (See "Universal Serial Bus Home Page[123]") Button[124] [Return to top[125]] ___________________________________ Where can I get a 16550 UART? If your 8250 or 16450 UART is a single chip mounted in a socket, it is easy to replace it with a 16550 UART chip. At the time of this writing WH Networks[126] was selling real 16550 UART chips for US$10 each. (Replacement of "multi-I/O" chips is usually not practical.) If you only need serial and parallel ports, Quickpath makes a good, albeit pricey, "multi-I/O" card called the "4 Serial 2 Parallel" that is available at retail (e.g., $100 at Central Computer in Santa Clara, CA, 408/248-5888), featuring: Four serial ports with high IRQ support that use real 16552 chips. Two parallel ports Quickpath also makes a more complete, albeit pricey, "multi-I/O" card called the "Port-Folio 550E" that is available at retail (e.g., $120 at NCA Computer Products in Sunnyvale, CA, 408/739-9010) Pros: Four serial ports with high IRQ support that use real 16552 chips Two parallel ports Four floppy support IDE and game port Con: Floppy support is only 1.44 Mb, not 2.88 Mb (inexcusable in a product at this price in the opinion of the author) Another good high-end "multi-I/O" card is the GSI Model 32, also available at retail (e.g., $120 at NCA Computer Products in Sunnyvale, CA, 408/739-9010). Pros: Two serial ports with (limited) high IRQ support that use a real 16552 chip One bi-directional parallel port Supports four floppies, up to 2.88 Mb (4 Mb unformatted), with drive remapping Enhanced IDE support for two drives (including large drives) On-board Flash BIOS Con: BIOS, IDE, and floppy support cannot be disabled A source of low-cost I/O cards with 16550-type UARTs is: Byte Runner Technologies 406 Monitor Lane Knoxville, TN 37922 voice: 800/274-7897 or 615/966-3667 fax: 615/675-3458 The "T-9004 Plus" ($32 plus a modest shipping charge) features: Two 16550-compatible serial ports (COM1-4) with high IRQ support One EPP/ECP bi-directional parallel port (IRQ 7 or 5) Supports two floppies, up to 2.88 Mb (4 Mb unformatted) Legacy header for (separate) PCI IDE controller But see warning below SIIG (Fremont, CA) makes I/O cards that are available at retail (e.g., $70 at Fry's Electronics in Fremont, CA, 510/770-3797). The "IDE Professional" (Model 2404) features: Two 16550-compatible serial ports (COM1-4) with high IRQ support One EPP/ECP bi-directional parallel port (IRQ 7 or 5) Supports two floppies, up to 2.88 Mb (4 Mb unformatted) IDE controller (hard disk or CD-ROM, primary or secondary channel) Game port But see warning below Pros of the Byte Runner and SIIG cards: High IRQ support makes it a lot easier to have a serial mouse and more than one modem. EPP/ECP parallel ports can be a lot faster than slow, old-style parallel ports. 2.88 Mb floppy support can make your "floppy tape" (e.g., HP/CMS Jumbo 250/350) twice as fast as 1.44 Mb. Con of the Byte Runner and SIIG cards: Both use the SMC[127] FDC37C666GT "multi-I/O" chip, which can cause lockups under Windows 3.1. (Warning: see "Why does Windows lock up when I try to access my modem?[128]") Button[129] [Return to top[130]] ___________________________________ Why am I getting CRC errors (overruns)? [updated 3/29/96] CRC errors (e.g., as reported by ZMODEM), particularly when downloading, are usually a sign of overrun (incoming data that is lost because the computer is unable to process it in time). Overrun can result from a variety of causes. The following are suggestions on how to avoid CRC/overrun errors (particularly in Windows 3.1): Use a 16550A UART. (See "Do I need a 16550 UART? What is a UART?[131]" and "Why does Windows lock up when I access my modem?[132]") (Most, but not all, internal modems use a 16550.) Use hardware flow control, and make sure it is working properly. This applies both to your modem and to your comm software. If you experience overrun while uploading, then you almost certainly have a flow control problem in your comm software and/or modem configuration. If you are running anything other than the standard Windows VGA driver, switch to the standard VGA driver and see if that affects your problems -- certain video drivers are known to interfere with communications. (See "Where can I get updated video drivers?[133]") If you determine that your video driver is causing overruns, check to see if your video card uses a recent S3[134] chipset (e.g., 864, 964, or 968). If so, there may be an option in the video driver to set "Bus-throttle=On" (usually Off by default) in the [display] section of SYSTEM.INI, which may well solve the problem. ("Bus-throttle=On" may slightly reduce speed as measured by benchmarks, but the difference will probably not be noticeable in the real world.) Contact the manufacturer of your video card. (Note: Generic S3 video drivers[135] are available from S3. Unfortunately, they do not work on all S3-based video cards.) [updated 3/29/96] If possible, use 32-bit disk access under standard Windows, as well as 32-bit File Access under Windows for Workgroups. If not, be sure you have a current version of a quality BIOS and/or disk driver. Watch out for poorly-written firmware and/or device drivers for local bus IDE interfaces, particularly in multi-sector mode. Obtain the latest versions. (You may be able to alleviate an overrun problem by switching modes and/or reducing the number of sectors per transfer.) Are you using a SCSI drive? Certain SCSI drivers can cause problems. Obtain the latest versions. Disable write caching on your download disk drive. (Read caching should be OK.) * With the current SMARTDRV (i.e., standard Windows, or Windows for Wordgroups without 32-bit File Access), the /X parameter disables all write caching. You can also disable write caching on individual drives. (See "SMARTDrive Drive Letter Parameters Should Not Contain a Colon[136]") * With 32-bit File Access under Windows for Workgroups, put the following in the [386Enh] section of your SYSTEM.INI file: ForceLazyOff=<drives> where <drives> is a drive letter string; e.g., ForceLazyOff=C for drive C only, or ForceLazyOff=CD for drives C and D. (See "How to Disable Write Caching for the 32-Bit File System[137]") If you are using Procomm Plus for Windows[138] 2.xx, set "DropRTSAroundDiskWrites=1" in your PW2.INI file. (This won't help if you cache writes.) Beware of TSRs, especially network TSRs. Try booting your system as clean as possible to see if that helps. Watch out for certain memory managers; e.g., the use of QEMM "Stealth" may cause problems. Put your modem on COM2 if possible, especially if you are using a serial mouse. (COM2 has higher interrupt priority than COM1.) Under Windows, put the following in the [386Enh] section of your SYSTEM.INI file: MinTimeslice=20 WinTimeslice=100,50 COMnFIFO=1 COMnBuffer=1024 where n is the number of your modem COM port (e.g., COM2FIFO=1 and COM2Buffer=1024). The COMnFIFO statement won't help until you get a 16550A UART, but it won't hurt in the meantime. Note: The only legal values for COMnFIFO are 0 and 1. (See "Windows Support of the 16550 UART[139]") Do not use Microsoft's PC speaker sound driver[140]! Get a cheap sound card instead. (The Logitech Factory outlet in Fremont, California, 800/231-7717, is a good place to get a cheap sound card.) Watch out for an IRQ conflict. (You normally cannot use both COM1 and COM3, or COM2 and COM4, at the same time.) On a portable or "green" machine, you should also try disabling the power management features, which can sometimes "kick in" and interfere with data communications. Disable any screen savers, which can interfere with data communications. Don't run your serial port any faster than necessary. Marketing hype notwithstanding, there's rarely any need to go faster than 38.4 Kbps with a 14.4 Kbps modem, or 57.6 Kbps with a 28.8 Kbps modem. Caveat: With an acknowledgment protocol (e.g., XMODEM), as opposed to a streaming protocol (e.g., ZMODEM), a higher serial port speed can improve the response time. Try a third-party replacement for COMM.DRV. (See What about third-party comm drivers for Windows?[141]) Switch to Windows for Workgroups or Windows 95, which have a better serial architecture than standard Windows 3.x. With a 16550 UART (See "Do I need a 16550 UART? What is a UART?[142]") under regular Windows and a third-party comm driver (e.g., WFXCOMM.DRV[143]) or Windows for Workgroups or Windows 95, try dropping the receive FIFO trigger level. For example, where n is the number of your modem COM port: * WFXCOMM.DRV (default 14): ComnRXSize=8 (e.g., Com1RXSize=8). Recommended setting. * Windows for Workgroups (default 8): COMnRxTRIGGER=4 (e.g., COM1RxTRIGGER=4). Legal receive FIFO trigger values are 14, 8, 4, and 1. The normal recommended value is 8. You should not go down to 1 unless you are really desperate. Button[144] [Return to top[145]] ___________________________________ <<cont>>