Search the FAQ Archives

3 - A - B - C - D - E - F - G - H - I - J - K - L - M
N - O - P - Q - R - S - T - U - V - W - X - Y - Z - Internet FAQ Archives

ZyXEL modem FAQ List v4.2, Nov 20 1995, Part 3 of 5 [Technical FAQs]

( Part1 - Part2 - Part3 - Part4 - Part5 - MultiPage )
[ Usenet FAQs | Web FAQs | Documents | RFC Index | Business Photos and Profiles ]

See reader questions & answers on this topic! - Help others by sharing your knowledge
Archive-name: modems/ZyXEL/FAQ/part3
Last-modified: 1995/04/09
Version: 4.2
Posting-frequency:  monthly;the third Monday of every month

                             ZyXEL Modems 
                           Frequently Asked
                            Questions List

                              Version 4.2

                    Archived at: in 
           Please mail any additions to:

Table of Contents

 T.      Technical Frequently Asked Questions
*T.1     What is the latest official ROM release(s)?
 T.1A    How does one determine the ROM revision?
*T.1B    What does one do if one does not have have the latest ROMs?
 T.1C    Where does one obtain EPROMs to update modem ROMs?
 T.1Ci   Will Toshiba EPROMs work?
 T.1D    What format are the ROM images?
 T.1E    What does one do with the latest ROMs?
 T.2     In which countries are ZyXEL modems certified to operate?
 T.3     What are known country codes?
 T.3A    How does one change a country code?
 T.4     What kind of power supply is used?
 T.5     Are ZyXEL modems Hayes-compatible?
 T.6     How do ZyXEL modems deal with escape sequences?
 T.7     What is the chip set / data pump used in the modems?
 T.7A    What is the advantage of this design?
 T.8     What is the meaning of the T401 and T402 timeouts seen in an "AT I2"?
 T.9     What is the selective reject in V.42?
 T.10    What is the "Capture modem manufacturer information" feature?
 T.11    What settings are required to attain the fastest data connection?
 T.12    Will V.32terbo be implemented?
 T.13    When will V.FAST (V.34) be available?
 T.14    Will V.34 fallback speeds be implemented?
 T.15    How does one patch GNU NetFax to work properly?
 T.16    Why doesn't faxing from WordPerfect work properly?
 T.17    Once a fax is received, what does one do?
 T.18    How does enabling callback security affect the reception of faxes?
 T.19    What is the easiest way to record voice?
 T.20    How good is the voice quality?
 T.20A   How does the voice quality compare versus the Rockwell chipset?
 T.20B   When will better quality speech at higher encoding rates be available?
 T.21    Can a voice call be detected by the modem?
 T.22    Are the specifications for converting voice files available?
 T.23    Can speech be digitized/recorded and played back simultaneously?
*T.24A   Can DTMF tones be recognized at any time during recording/playback?
*T.24B   Why is there a noise before a voice file is played through
         telco line ?
 T.25    What kind of problems exist with using voice software on Macintoshes?
 T.26    Why is there a slight hissing sound from the speaker?
 T.27    How does one make Caller ID (CID/CND) work correctly?
 T.27A   What exactly is the hardware modification needed for CID/CND and EDR?
 T.27B   What software modifications are needed?
 T.27C   What if CID/CND and EDR still doesn't work?
 T.28    What changes are needed for overseas calling?
 T.29    What modifications are needed to S/S+ models to get the eye pattern 

Subject:  T.  Technical Frequently Asked Questions

Subject:  T.1  What is the latest official ROM release(s)?
        1.04    For Elite 2864 model
        1.09    For Elite 2864I model

        6.15    For U-1496 modems with 1-Mbit EPROMs
        5.05c   For really old non-U-1496plus models 
	        with 1-Mbit and 512-Kbit EPROMs
        6.23    For U-1496P (portable) model

The ROM release previous to the 6.15 was version 6.14.  The latest quick 
reference card and the release notes for the latest ROMs can be obtained
via anonymous FTP from the Taiwan or USA FTP sites.

When a new official ROM revision is released, it is available for *ALL* ZyXEL
modems.  Thus when the 6.14 ROMs were released for the U-1494E modems, it
was also available for the E+/B/B+/S/S+ modems (and other ZyXEL models).

Beta ROMs have been known to ship in modems supplied by ZyXEL USA, so you 
may have a newer version than those listed here.

Subject: T.1A How does one determine the ROM revision? -------------------------------------------------------------------------------- For all ZyXEL modems: Type "ATI" in a terminal program. If the response is "1496", then type "ATI1" in the terminal program. (Alternatively, U-1496/U-1496S or U-1496+/U-1496S+ models can display the ROM revision via the product information screen.) Paul Platt ( writes: There is an easier way to get the firmware revision if you have an S or S+ model ZyXEL. Select the diagnostic display screen. Move all the way right. The firmware revision will show on the display. Note that you cannot always trust the corner arrow markers. They sometimes indicate that there is no "next screen" when a "next screen" actually exists. At some point, the response should have something like "U1496E V 6.13 M". The "V 6.13" indicates the ROM revision number (i.e. Version 6.13) The "M" character at the end indicates 1Mbit ROMs. The "K" character at the end indicates 512kbit ROMs. The "P" character at the end indicates that the modem is a "Plus" modem.
Subject: T.1B What does one do if one does not have have the latest ROMs? -------------------------------------------------------------------------------- The most convenient way to get the latest ROMS is to buy them. OCOMP, The Questor Project, ZyXEL USA (US$35), and others sell EPROMS with the latest EPROM release (cf P.9 or T.1.C). Another way to get the latest ROMS is to "make" a set. First, obtain two EPROMs (cf T.1C). Then, FTP the latest ROM image from a FTP site. (A complete ROM image consists of a pair of files. There is a pair of files for each of the E/E+/B/B+/S/S+ models.) Next, erase the EPROMs with an EPROM eraser (UV-light), verify the EPROM has been completely erased, and then use an EPROM burner to burn in the latest ROMs (cf T.1.D). Incorrectly programmed EPROMS will not work. The modem will compare the checksum of the chips with the checksum reported i the ATI1 command. If they are different, the modem will not function. Hint: Having two sets of ROMs around is a GREAT idea. Keep the old set that was in the modem, and install the latest ROMs. If a bug is found in the new ROMs, the old set can be re-installed. If the new ROMs are OK, then the old set can be erased, and reused to burn in the next ROM release.
Subject: T.1C Where does one obtain EPROMs to update modem ROMs? -------------------------------------------------------------------------------- Almost any major electronics supplier should be able to get the needed parts. You'll also need access to an (E)PROM burner capable of burning 1-Mbit EPROMs. Shop around for your EPROMs, as prices can vary drastically. ZyXEL does sell EPROMs for use in its modems. You need **TWO** EPROMs for a complete set of ROMs. ***BUY TWO EPROM CHIPS*** NOTE: Radio Shack doesn't count as a major electronics dealer. Part number to get: 27C010 1-Mbit EPROM 27C512 512-Kbit EPROM (really old non-plus's) Speed (of EPROMs) to get: |------------------------------------------| | non-plus models | plus models | |----------------------------------------------------------| | 512 kbit | 150 ns or faster | 100 ns required | |----------------------------------------------------------| | 1 Mbit | 150 ns or faster, | 100 ns required | | | 120 ns recommended | | |----------------------------------------------------------| John Weidman (dk139@cleveland.Freenet.Edu) has bought the 100ns EPROMs (part number TMS27C010A-10JL) from Newark Electronics (1-800-367-3573 in the US and Canada). Ackers Mattias ( has used "ST M27C1001" Signetics Thomson (??) 100nS EPROMs and they work fine with his E+ modem. Andrew Jackson ( has also used SGS-Thomson 27C1001 EPROMs. They work. In his experience, (but not confirmed) these devices apparently do not require the external links from Vcc to pin 1. They cost about NLG 18 each (about $9US) around September 1993. David Bowerman (1:153/290) [Fidonet] has used the Macronix 27C1000 and AMD AM27C010 parts as well with no problems being reported. You do have to be careful though since the part numbers for that size of EPROMs are a regular dog's breakfast. One company's 27C010 is another's 27C1000 and yet another's 27C1001 -- double check the cross references and make sure that the chip doesn't need the Vpp pin to be tied to Vcc (+5V) during normal operation. The ZyXEL modems don't even have a pin in the socket at that pin (1) -- a workaround is to solder a 22K resistor from pin 1 to pin 32. This allows the pin to be pulled high but doesn't allow enough current to flow during programming to cause problems -- at least the programmer I'm using doesn't seem to mind. Note for the inexperienced: Using faster ROMs will not make your modem go faster. The speeds recommended are those found to provide good reliability and operation and getting faster ones will not provide any further speed enhancement. Note for the lazy: Robert McKeever ( has purchased a large quantity of 27C010's and would be willing to sell some at a reasonable price (plus shipping) for those who don't want to shop around. E-mail him for details. Robert McKeever ( would even be willing to have them burned for a few bucks more. David Bowerman (1:153/290) [Fidonet] at Frog Hollow BBS in Port Moody, BC, CANADA, (604)469-0264 BBS (preferred), (604)469-9952 voice will burn a set of EPROMS. He is asking $5 if you supply the EPROMs, or $25 if he supplies them. His address is 112 Brookside Drive, Port Moody, BC, V3H 3H4. Please make sure that you state which modem model you have. Sean Foley (1:202/1609) [Fidonet] (18:701/1609) ZYXELnet at System Support BBS in San Diego, CA, USA, (619)563-9207 BBS, (619)563-9311 voice will burn a set of EPROMS. His address is 2869 Spruce St., San Diego, CA 92104, USA. He is asking for $5 (shipping included) with the exchange of the old set, or $25 (shipping included) for a new set. Please make sure that you state which modem model you have. The EPROMs are burned on new TI 27C010's that are matched to the speed of your ZyXEL model. Each EPROM is verified twice (buffer and CRC) before it is shipped. He will also include the release notes and such also. Wes Newell (1:124/7028) [Fidonet] at Wylie Connection in Wylie, TX, USA (214)442-0388 BBS will burn a set of EPROMS. He is asking for $5 (shipping included) for reprogramming the old set, or $15 (shipping included) for a new set. Please make sure that you state which modem model you have. Send him the modem model, the money, etc. at 1213 Devonshire, Wylie, TX, 75098 and he will send you a set of EPROMs with the latest ROM version.
Subject: T.1Ci Will Toshiba EPROMs work? -------------------------------------------------------------------------------- Dave Platt ( mentioned that although the Toshiba EPROMs are compatible with the EPROMs used in the ZyXEL in _most_ ways, and would work properly in _most_ circuits. Toshiba EPROMs are not 100% pin-compatible and won't work in the modem without a small hardware modification. To modify the Toshiba EPROMs to work in ZyXEL modems, Peter Nitezki ( wrote: The behaviour of Toshiba EPROMs is well known. They differ from Texas chips slightly, but the way ZyXEL uses them it's crucial. Toshiba chips (and many other) require Vpp to be at Vcc during normal operation. But ZyXEL leaves this pin open (no connector in the socket) as Texas chips don't need this. The solution is to solder a bridge from Vpp to Vcc pin, that has to be removed every time you want to program the chip. (IMPORTANT!!! Leaving the bridge in could damage the programmer circuit!)
Subject: T.1D What format are the ROM images? -------------------------------------------------------------------------------- Doug Kushner (71024.1643@CompuServe.COM) writes: ZyXEL EPROM images are in a binary format. However, if using a programming setup that supports multiple flavors of "binary", such as Data I/O's Promlink software, choose the "Absolute Binary" option. Soenke Behrens (behrenss@Informatik.TU-Muenchen.DE) and Brent Mosbrook ( [ZyXEL USA] explain that the ROMs are in binary format. They also mention that on most burners, you just load the file, identify it as a binary file, and specify the starting address of 0. David Bowerman (1:153/290) [Fidonet] mentions: Verify the EPROM against the file image, this is important as EPROMs do wear out after repeated cycling. Alan Brown ( writes: If an eprom fails verification, it should be placed under a standard eraser for a minimum 30 minutes, then reprogrammed using a slower algorithm. [This may be a way to "recover" a "worn-out" EPROM.] In all cases, eproms should be given "hard" (30 minute) erases every 10 reprogram cycles.
Subject: T.1E What does one do with the latest ROMs? -------------------------------------------------------------------------------- Do an "AT &V" and an "AT &Z?" in the terminal program. This will show the current active configuration settings on your modem. Print out this display. The information will prove to be handy should something go wrong, or should you decide to perform a hardware reset. Install them! Instructions are listed on page 15-16 and 15-17 of the ZyXEL User's Manual (Revision 2.1). [page 15-7 and 15-8 in the on-line version] Ensure that each ROM is inserted in the corresponding labelled socket. Jussi Torhonen ( talked to the local distributor who suggested that a hardware reset is advisable at this point. The hardware reset procedure is listed on page 15-15 and 15-16 of the ZyXEL User's Manual (Revision 2.1). [page 15-7 in the on-line version] The reset allows setup of the memory area reserved for new extended S-registers. The hardware reset will restore the factory default settings (but not the country code settings). To terminate the continuous analog loop test (the final phase of the hardware reset) momentarily depress the DATA/VOICE button on E/E+ models or use the front panel on S/S+ models. Barney Campbell ( notes that because the modem's default is set to a DTE speed of 38.4kbps unless the terminal is pre-set to that speed, the hardware test result will appear as garbage on the screen, because normally the DTE speed is detected by receiving an AT. However a test result is still "available" from the LEDs (U1496E/E+). To restore the modem to the settings before the hardware reset, re-input the results of the "AT &V" command. Barney Campbell ( notes that the stored phone numbers in the modem are also deleted in the hardware reset. To restore the modem to the settings before the hardware reset, re-input the results of the "AT &Z?" command.
Subject: T.2 In which countries are ZyXEL modems certified to operate? -------------------------------------------------------------------------------- Every country has telecommunication laws that prohibit the connection of unapproved telecommunication devices, including modems to the phone line. Approval by a country's telecommunications regulatory agency may entail hardware/firmware modifications to the modem in order to comply with telecommunication laws. This could include modifications for radio-frequency interference, pulse dial make/break ratios, redial capabilities, etc. The words "approved for use in country XYZ" mean that the modem *ITSELF* has been modified to comply with the telecommunication laws of that country. This means that an American FCC approved modem imported to Germany would not be a legal telecommunications device in Germany. The actual modem was FCC approved to work in the USA, but not BZT approved to work in Germany. No one can prevent the above scenario from occurring in any country. Possession of an unapproved device is usually not illegal. Attachment of the device, however, usually is illegal. It may result in confiscation of the device and/or financial penalties. [Non-approved ZyXELs have apparently been confiscated before in Germany. You are now cognicent of the albeit slim risks. Don't say that you were not warned.] [Rob MacKinnon ( adds that is is illegal to import unapproved telecommunications devices into Norway. Apparently the customs authorities will send the unapproved device back to the originator if it is found in the mail. If you happen to own an unapproved device, the state acting on behalf of Norske Telecom has the right to enter your house and confiscate the device because it is illegal to own one in Norway, not just use one.] [Tor Rune Skoglund ( adds: It is in fact illegal to IMPORT, SELL and USE non-certified modems here [in Norway]. Usually, the customs just skim through the invoice to see if there any word thats looks like "modem", and then they will refuse to deliver it.] Aside from the possible legal problems due to using an unapproved device, there are also some practical problems. Each ZyXEL modem operating its approved country has certain hardware modifications. These allow the modem to function better in the telecommunications environment for which it was approved. For example: German ZyXELs have a filter that eliminates the German cost-counting impulses. Polish ZyXELs have a reduced ring detector sensitivity that prevents voltage spikes from accidentally activating the modem. Should problems be encountered using an unapproved/uncertified ZyXEL modem, finding help may be difficult. The local vendor/distributor would be reluctant to help, as the product was not purchased from them. The original vendor/distributor might be difficult to reach. ZyXEL Inc. itself may not be too forthcoming, as product support costs are shifted to the parent company AND it encourages distributors to export product into another distributor's market (distributor turf-wars). Thus a ZyXEL modem operating in the country (for which it was approved) will work better than than an unapproved/uncertified ZyXEL modem. (Of course, your milage may vary.) Below is a list of countries in which ZyXEL modems have been approved for use. This list is *NOT* complete, nor exhaustive. If your country is not listed in this section, your modem may be approved for use in your country. This list is by no means definitive. Australia, AUSTEL approved Austria, OePTV (Oesterreichische Post- und Telegraphenverwaltung) Klaus J. Rusch ( writes: OePTV has approved the 1496E(+) ZyXEL modems, suffixed with the letter 'A' for Austria, for use as data modems. Fax and voice capabilities, as well as fax/data detection, are available yet not approved in the Austria models. The modems come with 3 meter TDO cables, ZFAX software and 220 V 50 Hz power supplies. Similar to Germany's 1496EG(+), the 1496EA(+) must establish a connection within twelve tries. Failure to do so causes the modem to block, and require a manual reset (power off/on). Any request to connect (ATD) is answered with 'STOP !'. Note: Setting the country code to 233 has the same effect with the 1496E+ model. Czech Republic, Czech Telecom The Zyxel U-1496E has been approved on September 16, 1994 for operation on telephone lines of Czech Telecom. The certification number is 15579/94. Canada, Department of Communications (DOC) approved Model Name Certificate No. Certification No. Load No. U-1496 9165 1817 4783 AB 11 U-1496E 9166 1817 4783 AB 11 U-1496B 9167 1817 4783 AB 11 U-1496R 9168 1817 4783 AB 11 Germany, (BZT) Eelco H. Essenberg ( writes: I just read the september issue of the German computer magazine c't. It appears ZyXEL has obtained BZT certification for a model called "U-1496EG Plus". This basically is the E+ with a metal housing. Pulses for pulse-dialing are no longer generated by a relays, but electronically. A filter eliminates the german cost-counting impulses. Automated redialing has been changed (suppressed) according to german telecom rules. [Minimum time between 1st and 2nd try: 5secs; " " " 2nd " 3rd try: 60secs; No more than 12 tries to the same number if no answering tone is received; After 12 failed tries, a minimum waiting time of 1 hour before attempting the same number.] Sufficient changes have been made so that this beast will only accept ROM updates specially designed for it: no chance of reversing the redial disability this way :-(. Also, the second RJ11 jack, the one in which you connect your phone, has been removed. Worst: while the normal E+ costs around DM900, this thing is expected to cost close to DM1400. In Germany one can buy the 1496EG+, the telecom-certified version of the 1496E+ which has some diffences to the original 1496E: *The case is metallic *There is a mechanism implemented which delays and stops redialing after several unsuccessful dials. *ROM-Updates are allowed, but only with certified releases. *Impulse-dialing is _much_ more silent *It's much more expensive (around 1350.- DM) Japan, Japan Approvals institute for Telecommunications Equipment (JATE) Japanese PTT approval is now underway. New Zealand, U-1496S, PTC 211/92/035 Alan Brown ( adds: In New Zealand, a "Telepermit" is issued to the *importer*. If another importer decides to start carrying an item, even if it's factory modified for NZ, it must be resubmitted by the new importer. On the flipside, "Telepermits" are cheap - NZ$2000 (~US$1050) and include all laboratory test costs. Poland, Ministry of Communications U-1496E, Polish homologation certificate no. 421/93 U-1496S+, Polish homologation certificate no. 513/93 ZyXEL is probably the only, reasonably priced modem capable of coping with the mediocre Polish telephone lines. That comes with a price, however. ZyXEL modems sold in Poland are a bit different than FCC version, and of course more expensive. Changes: 1) Reduced sensitivity of ringer detector, so no accidental spikes in telephone lines will activate the modem. 2) Higher input impedance, as required by the telecommunications regulations. 3) Considerably higher DTMF level (than in the FCC model). While the third modification is relatively easy to implement, through the replacement of the ROM(s), the other two require significant hardware change. Scientific [a Polish dealer of ZyXEL and Zoom modems] is authorized by ZyXEL to make such changes, including ROMs replacement as well. Switzerland, Federal Office for Telecommunication (BAKOM) The present homologation status is shown below. Any modification (technical characteristica, hardware, firmware, etc.) requires re-certification. Model Speed HW SW BAKOM # U-1496 14.4K ? V+ 92.1148.D.N U-1496B 14.4K Rev-5A V5.02 93.0076.D.N U-1496E 14.4K ? V4.09 92.1149.D.N U-1496E+ 16.8K Rev-B2 V5.04 93.0155.D.N U-1496E+ 16.8K ? ? 93.0204.D.N * * this modem was submitted by another importer which no longer sells it A general note : voice functions are not agreed by BAKOM USA, Federal Communication Commission (FCC) approved Model Name FCC number REN# Class U-1496 1ROTAI-18563-MD-E 1.1B A U-1496B 1ROTAI-18518-MD-E 0.8B A U-1496E 1ROTAI-65020-MD-E 0.5B B FCC# I88U1496E Denmark Finland Hong Kong Iceland Indonesia Ireland Russia Singapore Sweden Thailand Turkey
Subject: T.3 What are known country codes? -------------------------------------------------------------------------------- Country codes customize ZyXEL modems to work better in a particular country. A ZyXEL modem operating in the country for which it was approved for use, should leave its country code unchanged. Austria: 233 Australia: 244 Belgium: 248 Czech Republic: 246 Denmark: 252 Finland: 240 Germany: 237 Greece: 247 Holland: 253 Hong Kong: 242 Hungary: 229 Japan: 234 Malaysia 241 New Zealand: 243 North America: 255 Norway: 245 Poland: 231 Singapore: 241 Slovakia: 228 South Africa: 254 Sweden: 250 Switzerland: 251 United Kingdom: 249 ZyXEL USA does not confirm nor deny the existence of country codes. Thus they can not confirm if any entry in the above list is correct. [Note that ZyXEL would get into big trouble with the local telecommunications authority if people suddenly started to import large numbers of non-approved modems into the country.] If you know of any other country codes, please mail them to Robert Wong ( for inclusion in a future version of this FAQ.
Subject: T.3A How does one change a country code? -------------------------------------------------------------------------------- To get the current country code (North America = 255), type: AT#H Write down this country code, in case the new country code does not work properly. Follow these steps to change the line interface to match those used/required for operation in various countries. Type: ATS38.1=1 AT#G123 where 123 is the country code desired. AT&W to save these settings Probably best to power-cycle the modem at this point. Again, a ZyXEL modem operating in the country for which it was approved for use, should leave its country code unchanged. Changing the country code in a ZyXEL (for use in that specific country) SHOULD theoretically improve its operation. There have been reports to the contrary. If problems occur from using a new country code, reverting to the previous country code might be advised.
Subject: T.4 What kind of power supply is used? -------------------------------------------------------------------------------- ZyXEL uses a transformer that is a 120V AC, 60Hz, 23.4W model that outputs 20VAC, 900mA with a center tap. The transformer should ideally have output between 50 Hz and 60 Hz. +-----+ AC --> | o o | <-- AC \ o / --- ^ +-- Center tap Michael Chua Boon Wei ( has a power supply that is a 240V AC, 50 Hz, 27.5W model that outputs 21V AC, 900 mA. It has the same pinout as above. Michael Kuhl ( and Robert Wong ( has a slightly different power supply that is a 120V AC, 60 Hz, 12.5W model that outputs 9V AC, 1000mA. It is also described as a Class 2 Transformer, Part No. 30-111-011496, Model No. A48091000 transformer. Also, the pinout is slightly different. +-----+ AC --> | o o | <-- No connection \ o / --- ^ +-- AC Alan Brown ( has a power supply (non-ZyXEL) that is a 230V AC, 50 Hz model that outputs 14V AC. The shape of the connector is a cylindrical 2.5mm coaxial power socket seen on many other pieces of electronic equipment. ZyXEL modems seem to accept many different voltages ranging from 9 to 20V AC. The output voltage for the transformers may be as low as 5V AC. Also, the power supply may or may not be center tapped. Also, in countries with 220V AC, the local suppliers supply a locally manufactured power supply. To avoid any potential problems, use only the power supply that came with the modem. ZyXEL does sell power supplies for owners should they move to another country or lose the factory power supply. Please e-mail Robert Wong ( if you have a different power supply.
Subject: T.5 Are ZyXEL modems Hayes-compatible? -------------------------------------------------------------------------------- Yes, ZyXEL modems are Hayes-compatible. ZyXELs use the same basic AT command set used in the 2400 baud Hayes Smartmodems. ZyXELs have an enlarged and enhanced AT command set in addition to the basic AT commands common to the 2400 baud Hayes Smartmodems. These additional commands deal with higher baud rates, fax settings, voice settings, and other features that were not present in the original AT command set of 2400 baud Hayes Smartmodems.
Subject: T.6 How do ZyXEL modems deal with escape sequences? -------------------------------------------------------------------------------- Byte Magazine, V18, N8, July 1993, pg 184 has a good background article about escape sequences. The information below is a less technical explanation of escape sequences. An escape sequence switches a modem from transmission mode to command mode. Sometimes, an AT command needs to be issued to the modem when it is on-line and connected with another modem. Since the modem is on-line, typing an AT command would send the AT command down the connection to the other modem. Thus the local modem never receives and acts on the AT command. An escape sequence is needed to bring the local modem into command mode (without dropping the connection to the other modem). One escape sequence is to drop the DTR (Data Terminal Ready) signal on one of the wires in the serial cable. This is a reliable escape sequence. Some hardware platforms do not have a wire for the DTR signal and therefore cannot perform this escape sequence. Another type of escape sequence is needed. An alternate escape sequence is a pause, followed by three escape characters, and then another pause. This escape sequence then puts the modem into command mode, allowing entry of AT commands. (The pauses prevent the modem from mistaking escape characters in the data stream for "true" escape characters in an escape sequence.) Hayes has a patent on the pause, escape characters, and pause technique. Other modem manufacturers are required to pay royalties to Hayes for use of its patent. Some modem makers are not using the Hayes patent or any other method of distinguishing real escape characters. This causes factory configured modems from these modem manufacturers to inadvertently go into command mode when the Hayes test file is transmitted. Taken from Byte Magazine, V18, N8, July 1993, pg 184 without permission: "Zyxel [sic] has its own algorithm, for which it claims compatibility with existing code. Since the Zyxel [sic] algorithm is proprietary, we can't comment on its strength or weakness. However, it caused no problem in our testing." Taken from BoardWatch Magazine, V6, N9, November 1992 without permission: "To illustrate the technical elegance of this [ZyXEL] modem, recall our article on the Hayes brouhaha over their fixed guard time escape sequence under the Heatherington 302 patent. Hayes has licensed numerous modem manufacturers to use this escape sequence. A few have not licensed it and often, their modems will escape to command mode while transmitting files containing +++ escape sequences. Hayes caused something of a furor in July by releasing a text file that if transmitted by many modems that don't use the guard time escape sequence technique, would abort the transfer and improperly escape to command mode. Multitech's modems fail the test rather awkwardly. The ZyXEL modem does NOT license the Hayes escape sequence. According to Gordon Yang, they use a proprietary variable sampling algorithm that does the job at least as well. We tried the ZyXEL on the Hayes test file - and sure enough, it worked like a champ. ZyXEL appears to have engineered a way around the escape sequence controversy. Yang indicates that they could conceivably publish the algorithm. If they did, this would take some serious steam out of the Hayes licensing program."
Subject: T.7 What is the chip set / data pump used in the modems? -------------------------------------------------------------------------------- ZyXEL models do *NOT* use the Rockwell chipset. ZyXEL uses their own code, which runs on a Motorola 68000 processor and two Texas Instruments Digital Signal Processors (DSP). The DSPs used are the same type seen in US Robotics modems. Barney Campbell ( asks: "What is the data pump on the ZyXEL modem? PC magazine 1993 June 29,Vol 12, No 12 p 272 reports that the U-1496S+ uses a Texas Instruments data pump and that the U-1496E uses a ZyXEL data pump. Is this correct? If different data pumps are used in each model, then the S+ might be OPERATIONALLY different from the E models. Namely, they might perform differently." Brent Mosbrook ( [ZyXEL USA] replied stating that the Texas Instruments and ZyXEL data pumps behave identically. The DSPs were re-done to eliminate the daughterboard on some models. The models without the daughterboard have DSPs which say ZyXEL, while the daughterboard equiped units say TI. Again, there is no real difference and they behave identically.
Subject: T.7A What is the advantage of this design? -------------------------------------------------------------------------------- Again, ZyXEL modems do not use a chipset. The main advantage to not using a chipset is upgradability. New features and bugfixes can be easily "installed" into the modem. Kolja Waschk (kawk@Yo.COM) adds: "Anyone who has an EPROM-burner might download the newest firmware from a ftp server or public mailbox (many sites available) and put it in his modem. Just remember, the ZyXEL's haven't been "voice capable" some months ago, but now they are - without any hardware changes." Brent Mosbrook ( [ZyXEL USA] also writes (with a great deal of marketing-speak): "The ability to independently design hardware/features is probably the #1 advantage. We have been able to add many new features to the basic modem through rom upgrades. (CID, Distinctive ring, Voice, EDR, etc.) Also, as shown in the past (E --> E+ upgrade), the modem can be upgraded by modules. The key components of the modem (CPU, DSP, ROMS) can be updated/replaced individually. This allows greater flexibility in adding new hardware capability to existing products. As stated here in the past by others, a modem vendor who can design the product from the ground up generally has a higher caliber engineering dept. They can respond quickly to bug reports, and have a better understanding of what makes the product tick. A chipset based vendor is completely dependent upon their source for most bug fixes, and there is no guarantee that the modem vendor is capable of implementing the chipset as designed (even with written instructions from the manufacturer. :)) Bottom line: there is no guarantee that a DSP based modem is any better than a chipset based modem... The proof is in the end-result. Take a look at the reviews, and comments of current users to evaluate a modem.. These should be part of your selection criteria, in addition to the DSP/Chipset used."
Subject: T.8 What is the meaning of the T401 and T402 timeouts seen in an "AT I2"? -------------------------------------------------------------------------------- On page 15-13 of the ZyXEL User's Manual (Revision 2.1), [page 15-6 in the on-line version] it says that the T401 and T402 timeouts "are normally zero". Often these values are not zero. T401 and T402 are the name for two timers that are used in MNP 4 and V.42 connections. The values for both timers are set during the initial handshake. The T401 is the acknowledgement delay timer that monitors the amount of time between the sending of a data block and the receiving of an acknowledgement. The T402 is an inactivity timer which monitors the time between data blocks sent to the receiver. The terms "T401 Timeout" and "T402 Timeout" refer to the number of timeouts in the T401 and the T402 timers, respectively. (A timeout is a "timer expiration" and is the result of an action not being performed in a given allotted time.) Brent Mosbrook ( [ZyXEL USA] writes: The "T401 Timeout" indicates the number of resent blocks, due to not receiving an acknowledgement in the allotted time. The T401 timeout is just one of the reasons for blocks being resent, so T401 timeouts will not necessarily be equal to the BLOCKS RESENT value in a link status report. The "T402 Timeout" indicates the number of frames sent due to inactivity. These are sent to keep the link active, and assures the other modem that the connection is still there. This number steadily increases, especially during a relatively "light" interactive dialup session.
Subject: T.9 What is the selective reject in V.42? -------------------------------------------------------------------------------- Selective reject is an optional feature of the V.42 error correction protocol. The v6.10 ROMs were the first ZyXEL ROMs that implemented selective reject. Brent Mosbrook ( [ZyXEL USA] writes: Selective reject is an optional feature of V.42 which allows you to get higher throughput on noisy lines. The modem sends out blocks, and the remote side acknowledges after an agreed upon number of blocks (window size). If one of these blocks is bad, then the modem will only send the bad one over again, rather than all the blocks (as is the case of other modems). The selective reject feature only works when both modems implement it. Thus a ZyXEL with 6.10 ROMs will not use selective reject connected to a ZyXEL with 6.01 ROMs. When in use, the initial connect string will look somewhat like "CONNECT 57600/ARQ/V42b/SREJ" (the exact string varies depending on the AT X[0-7] setting). Chris Gray (cgra@btma74.nohost.nodomain) explains that selective reject is an optional part of the LAPM protocol used by V.42 modems. A SREJ frame requests retransmission of one information frame, having the sequence number which is cited in the SREJ frame; after this transmission resumes _from where we left off_. Contrast with ``ordinary'' REJ, which requests retransmission of _all_ information frames, starting with the one with the specified sequence number. SREJ is more efficient when just one frame has got munged. information(4) -------------------------------------------> information(5) ------------------------------ (bad CRC) information(6) -------------------------------------------> uh uh, we've lost 5 SREJ(5) <------------------------------------------- information(5) -------------------------------------------> that's better information(7) -------------------------------------------> etc., as opposed to: information(4) -------------------------------------------> information(5) ------------------------------ (bad CRC) information(6) -------------------------------------------> uh uh, we've lost 5 REJ(5) <------------------------------------------- information(5) -------------------------------------------> that's better information(6) -------------------------------------------> yes I knew that information(7) -------------------------------------------> Note that SREJ causes some problems when handshaking with modems not supporting SREJ. This is not a bug in ZyXEL modems. Shutting off SREJ will avoid the handshake problem.
Subject: T.10 What is the "Capture modem manufacturer information" feature? -------------------------------------------------------------------------------- ZyXEL modems will capture the name of the remote modem when bit 1 of S-register 13 is enabled (AT S13.1=1). This information is obtained during the V.42 handshake sequence. Since the information is an OPTIONAL feature, it will only work when the remote modem has also implemented this feature. Some, but not all manufacturers have implemented this feature. When this information is captured, it is then shown via the ATI2 command, in the "Last Speed/Protocol" field. The following is an incomplete list of possible modem manufacturer information: Information Remote modem type ZyXEL ZyXEL modem Flash ZyXEL modem CODEX Motorola Codex Dig Digicom modem HST USR Courier modem SOF Tornado V32B/Fax modem ST LongShine 9600M5/Fax modem Please e-mail Robert Wong ( if you have seen any other remote modem types.
Subject: T.11 What settings are required to attain the fastest data connection? -------------------------------------------------------------------------------- To obtain the fastest data connection for a ZyXEL, a number of steps should be taken: a) Lock the serial port speed to the fastest/highest speed supported by the host computer. b) Turn off "auto-baud detect", "dial speed-matching", or any similar parameter. c) Turn on hardware flow control by enabling RTS/CTS flow control in the communications program. d) Turn off software flow control by disabling XON/XOFF flow control in the communications program. e) Turn off DSR/DTR hardware flow control, as this is used for null modem connections. (Recommended if the communications program supports this feature.) f) External modem owners must use a modem cable that is wired for hardware flow control. Notes: 1) Again, the modem cable MUST be wired correctly. Apparently, some modem cables, even from the factory, are not wired properly for hardware flow control. Alan Brown ( adds: I find that it's generally a good idea to switch the modem to CCITT DSR (AT &S1), even though no programs I use support this for flow control. In CCITT mode, DSR comes up before the CONNECT message (actually as soon as a link standard is established, even though error correction may still need to be negotiated), and goes down after NO CARRIER
Subject: T.12 Will V.32terbo be implemented? --------------------------------------------------------------------------------- ZyXEL USA's response: V.32terbo is not a CCITT (ITU-TSS) standard, and does not perform as well as 19.2ZYX. We will have to see a greater popularity of V.32terbo to support it.
Subject: T.13 Why Aren't the Elite models upgradeable to V.34+? -------------------------------------------------------------------------------- No, the Elite models are *NOT* upgradeable to V.34+. V.34+ isn't an international ITU-TSS standard. Currently, it is a modified version of the V.34 standard. Most Elite users would probably like to be able to upgrade their Elite to V.34+ via a simple flash ROM upgrade. Unfortunately, it isn't possible. Some Elite users are upset about non-V.34+ upgradeability. Please keep a couple of points in mind: a) ZyXEL never advertised that the Elite was V.34+ upgradeable. They said that the Elite was built to take advantage of the new generation of "modem" technology. i.e. The Elite could be upgraded to faster speeds. ZyXEL meant upgrading to ISDN, rather than upgrading to V.34+. [Editor's Note: Unfortunately, many people (myself included) interpreted the word "upgradeability" the way we want to interpret the it. We read what we wanted to read and we saw what we wanted to see. Sad, but true. ZyXEL never promised something (V.34+ upgradeabiltiy) and didn't deliver it.] b) Since, V.34+ is not a true internationally approved standard, it may be yet another flash-in-the-pan. ZyXEL did not support V.32turbo, or V.FC. Both of these were non ITU-TSS approved standards. Users screamed at that time. Both V.32terbo and V.FC protocols support became non-issues as they were superceded by the ITU-TSS approved V.34 protocol. Hopefully, V.34+ will die a quick death. ZyXEL USA's response: "ZyXEL Elite Owners At a time when our competitors were beginning to introduce their V.34 products, ZyXEL was already planning to take our users beyond V.34 into the unexplored frontiers of ISDN. ZyXEL has always been on the forefront of technology - and it is not a title we intend to relinquish anytime soon. Recent inquiries from Elite modem users have brought to our attention some concerns regarding the 33.6 Kbps speeds available now with some of our competitors' products. We feel it necessary to inform our users that we do not have plans to upgrade the Elite Series to 33.6Kbps (V.34+). 33.6K speed relies heavily on the bandwidth of the telephone carrier which might be hard to find in the real world phone line. The Elite 2864 has been designed from the onset as a transitional product from V.34 to ISDN. We have chosen, in this product, to focus on ISDN because digital technology is where the modem market is headed. The Elite 2864 was designed specifically for users who could potentially take advantage of what ISDN has to offer, but who needed V.34 speeds now. We have concentrated our hardware development on offering better ISDN capabilities. As a result we are proud to be able to offer features like V.42bis Data Compression over ISDN and Channel Bundling - two features which ZyXEL was one of the first to introduce. Additional enhanced features of the Elite 2864 set ZyXEL apart - product features like the flexibility provided by Serial and Parallel ports, the standalone fax feature with direct printing, DES encryption, Kernel Recovery Mode and larger firmware and DRAM storage space. We are also planning to support additional popular standards like multi-link point-to-point(MP) protocol and new Internet communication protocols. Competition has yet to offer these features in a single device. As a result of development hurdles, our entry into the V.34 market has taken longer than expected. But we are moving full speed ahead to improve product performance and reliability to make up for the lost time. We are confident that the finished Elite 2864 will be a product to meet all your expectations. Our mission always has been and always will be to take you to the cutting edge of technology - not to make quick sales on overnight trends which are here today and gone tomorrow. As always, we appreciate your continued support of ZyXEL and your valued feedback. Should you have any concerns about your Elite 2864 modem or have additional questions, please contact us directly at 800-255-3160. ZyXEL Customer Service Marketing Department Fax: 714-693-8811 ZyXEL Web:" Robert Wong ( writes: "ZyXEL USA is the main contact point for North and South American ZyXEL owners. Should you have any concerns about a ZyXEL product, try contacting your local dealer and then your local ZyXEL distributor." Winston Edmond ( "According to posts in this newsgroup, Motorola Power modem owners have recently been told by Motorola that: * V.34+ capable versions of the Power modem will come out in January, * current modems can't be upgraded to V.34+ despite flash ROM (hardware too slow), and * there's no upgrade path for current owners. Sounds familiar [to ZyXEL Elite owners], somehow, doesn't it?"
Subject: T.14 Why Can't the Elite models always connect at 28.8kpbs? -------------------------------------------------------------------------------- Byte Magazine, V20, N11, pg 40 has an article titled "Telecommunications: Phone Lines Stymie V.34 Modems. That spiffy new V.34 modem may feel like a station wagon instead of a turbocharged racer. Here's why." It mentions that V.34 modems are supposed to communicate at 28.8 kbits/s, however most people will not get more than 26.4 kbits/s except under prime conditions. Apparently, equipment used to reduce static, interoffice phone systems, digital speech compression, etc. reduces the top speed of V.34 modems. The article makes a couple of negative remarks about early USR Sportsters, and Rockwell chipset modems. It also mentions that consistent fast data connections are achieved via ISDN. Overall, this article is quite informative about the barriers to 28.8 kbits/s data transmission. Robert Wong ( writes: "There was some debate in the comp.dcom.modems newgroup about the connection speed of the ZyXEL Elite modems. The consensus seemed to be that the ZyXEL had slower initial connection speeds when compared with the USR modems. Some posters vehemently stated that the ZyXEL was substandard. Personally, I have had my ZyXEL Elite for about 1.5 weeks. I have had a grand total of 64 connections. 3 (4.7%) of the connections were at 28.8 46 (72%) of the connections were at 26.4 15 (23.4%) of the connections were at 23.4 From my very limited experience, I don't often get 28.8 connections. About 70-75% of the time, I get 26.4 connections and about 25-30% of the time, I get 23.4 connections. Note these are merely *initial* connection speeds. I have not looked at connection speeds over time. They may have gone up, stayed the same, or gone down during my connect sessions. I haven't checked, thus I don't know the answer. The current v1.04 ROMs are pretty stable. Hopefully in future ROM releases, ZyXEL can work on increasing and maintaining the initial connect speeds. ZyXEL has has a pretty good track record for improving their modems. They be able to address this and other concerns with succeeding ROM releases."
Subject: T.14 Will V.34 fallback speeds be implemented? -------------------------------------------------------------------------------- The V.34 specification currently calls for fallback speeds of 16.8 and 19.2 kbps. Some people have thus inquired about the possibility of implementing the 16.8 and 19.2 fallback speeds (in the the current ZyXEL modem line). ZyXEL USA's response: The specifications for V.34 call for a multiple carrier frequency during a connection ie. multiple baud rates. ZyXELs currently can only do a fixed baud rate during a connection. If the specifications are modified to not use shifting baud rates, then it may be possible. If the specifications remain unchanged, ZyXEL *MAY* implement V.34 fallback speeds. If and only if ZyXEL decides to implement the fall back speeds, the work would BEGIN only *AFTER* the new modems ship.
Subject: T.15 How does one patch GNU NetFax to work properly? -------------------------------------------------------------------------------- Receiving: Receiving works flawlessly, PROVIDED that you convince Netfax to send 0x12 instead of 0x11 to the Zyxel when starting to receive a new page. Apparently the standard changed this over two years ago, and most other modems still also accept 0x11 as a compatibility kludge. Sending: The key to sending multiple pages is to throw out AT+FDT=a,b,c,d and replace it with AT+FDT, and to set the desired parameters in a AT+FDCC=a,b,c,d,e,f,g,h message sent when starting up. A pre-made set of patches is available from as a file called netfax.patches
Subject: T.16 Why doesn't faxing from WordPerfect work properly? -------------------------------------------------------------------------------- Both WordPerfect and ZyXEL are aware of the problem. Carl Oppedahl ( writes: If WordPerfect customer support can be believed, there is a programming error in the ZyXEL firmware. WP has supposedly been in communication with ZyXEL to urge them to make the modem recognize semicolons. Brent Mosbrook ( [ZyXEL USA] acknowledged the bug and "we are testing the fix right now, and will release it in approximately a week." The problem has apparently been fixed in the v6.11 ROMs. Problems were only encountered in the high resolution modem, but not in the standard resolution mode.
Subject: T.17 Once a fax is received, what does one do? -------------------------------------------------------------------------------- A fax is received by the ZyXEL modem and fax software. The fax (usually) is stored as a file on the hard disk in some sort of image format (TIFF, PCX, etc.). This file is called a "fax image". The fax software or some other software program can be used to open and print the fax image. To put the contents of the fax into a word processor, there are two options: a) The fax image could just be imported as an image into the document. This is not a good solution, as the contents of the fax cannot be edited and the image itself may not be too clear. b) A better alternative is to use a software package that has an Optical Character Recognition (OCR) capability. [OCR may be built into the fax software, or it may be a separate software package. Retrieve the fax file into the OCR software and use the OCR software to convert the fax IMAGE into an ASCII file.] Import this new ASCII file into the word processor. In this manner, the fax image was OCR'ed and is now in a clearer, editable format on the word processor. Alan Brown ( adds: For some reason the PCX images generated by ZFAX 2.xx are not readable by some graphics packages. DISPLAY, Graphics Workshop (all dos versions) and VPIC (all versions) definitely refuse to display/edit ZyXEL PCX files. The author of DISPLAY is apparently looking at the problem.
Subject: T.18 How does enabling callback security affect the reception of faxes? -------------------------------------------------------------------------------- Incoming fax transmissions will not be prompted for a password when the security function AT *Gx is enabled. Thus reception of faxes is unaffected by the enabling of security passwords/callbacks.
Subject: T.19 What is the easiest way to record voice? -------------------------------------------------------------------------------- One method of recording voice on a ZyXEL modem is from another phone line. This method is useful if two phone lines are present. Another method of recording voice on a ZyXEL modem is to speak into the *earpiece* of a telephone handset, which is attached to the line connector of the modem. This technique is may not be too effective. ZyXEL is now shipping a hardware device/box which will make voice recording with a ZyXEL much more effective. The modem plugs into the box, and the phone line is plugged into the box. A switch on the box allows recording directly from the phone. This box has the amplifiers built in to record from an un-powered phone. No plug-switching necessary. The ZyVoice box is now shipping and sells for US$30.00. Paul Dowling ( writes: "I was skeptical to say the least that this solution [the hardware box] would work. Well, it works MUCH better. I've only played with it for a few minutes, but there is a definite improvement in the quality. It's still not as good as I'd like, and there is still a slight whining noise in the background, but this seems to really have worked. The switch box includes a power converter and 2 RJ-11 wires. There is a button next to the dial-up line connection that allows you to select between voice and normal. The other side has jacks to connect to the phone and wall lines on the modem and to your telephone. The box is about 3 1/2" x 2 1/2". I don't like the idea of having an external box and I hope in the future they will build it into the board, but for now, I'm very pleased with it."
Subject: T.20 How good is the voice quality? -------------------------------------------------------------------------------- Saurabh Misra ( writes: "Horrible is not an objective description [of voice quality]. If you realize that the voice compression algorithms used in ZyXEL modems are meant for telephonic use then you will find the quality quite good. If you are expecting voice quality that compares to that of a radio receiver tuned to a strong channel, then you will find the voice quality 'horrible'. Basically, the voice quality (especially ADPCM3) is very good and completely acceptable for telephone use. As far as the caller is concerned, he won't know the difference between the ZyXEL's outgoing message voice quality and that of an answering machine. This is assuming ADPCM3. ADPCM2 and CELP are significantly deteriorated versions of ADPCM3." Brent Mosbrook ( [ZyXEL USA] writes: "Voice quality can vary depending on a couple factors: 1) recording format (4-bit ADPCM is best sounding) 2) recording method (remote phone, local handset, etc) To eliminate the need to unplug your handset and phone line (current method to record msgs locally), we have released a switch box, which will allow you to plug in your telephone, modem, and phone line to the box, and then hit a toggle switch to record and playback your messages through the TELEPHONE, rather than just the handset." Kolja Waschk (kawk@Yo.COM) writes: "I believe it's a problem with the quite simple coding algorithms used in the ZyXEL." (c.f. T.18A) Apparently, better voice quality is forthcoming. To improve voice quality, the number of bits and/or the sample rate could be increased. (c.f. T.19B)
Subject: T.20A How does the voice quality compare versus the Rockwell chipset? -------------------------------------------------------------------------------- Kolja Waschk (kawk@Yo.COM) writes: "Rockwell chipsets do higher quality voice replay. This may be due to the fact that they use a slightly more complicated ADPCM enconding or due to the fact, that - in addition to ZyXEL modems - Rockwell chipsets are capable of encoding the signal using 4 bits per sample. However, the RW chipsets do the sampling at 7200 Hz, the ZyXELs do it at 9600 Hz; that make me believe that the quality difference depends mostly on the coding algorithm (and tables) used. On ZyXEL modems, it's nearly impossible to record voice without any digitally generated background noise; on those Rockwell equipped modems which I have seen (heard), it IS possible."
Subject: T.20B When will better quality speech at higher encoding rates be available? -------------------------------------------------------------------------------- 4-bit ADPCM was introduced in 07-05-1994, with v6.13 of the ZyXEL ROMs. The increased number of bits improves the voice quality noticeably. Brent Mosbrook ( [ZyXEL USA] adds: "Currently, the sample rate is 9600 samples/second. 3-bit ADPCM requires the DTE speed to be 38.4K." The new 4-bit ADPCM requires a 57,600 DTE speed. Question Q.10 mentions that there will be a faster DTE rate in the next generation of modems. This raises the possibility that even higher encoding rates may arise in the future.
Subject: T.21 Can a voice call be detected by the modem? -------------------------------------------------------------------------------- The modem itself cannot distinguish between an incoming fax/data/voice call. With software, it is possible to discriminate between a fax/data/voice call. Kolja Waschk (kawk@Yo.COM) [writer of the ZuTSR and ZUtil] writes: "The modem itself cannot discriminate between a fax/data/voice call. Voice calls do not differ from normal data calls (assuming most calling modems do not send a calling tone). However, the modem can be told to answer in Voice Mode, and then "listen" what's on the line. It can detect several possibilities, ie. "fax calling tone heard", "modem calling tone heard" (since firmware 6.11), "DTMF tone Nr.x heard", and, while in record mode, "caller keeps silent" or "caller made some noise and then turned silent". It's the software on the computer that should react differently on these reports and switch the modem into data/fax mode respectively. Two programs are known to do more : VoiceConnect and the (not yet released) new ZUtil do real-time signal analysis on the incoming voice data and can detect - in addition to the above mentioned events - the presence of "human voice". The most used method to distinguish between data and voice calls is the following (flow controlled by the software on the computer) 1. answer the line 2. replay play a spoken greeting message, provoking voice callers to speak (a small "Hello?" does the job) 3. listen 4. switch to data/fax mode if a calling tone has been received 5. switch to data/fax mode if the caller keeps saying nothing [The call is not conclusively proven to be a data call, but it is reasonably assume to be a data call. Ed.] 6a. handle the voice call if "voice" (only with VC or ZUtil) has been detected or simply the caller does not remain silent and does not sent calling tones. 6b. handle the voice call if the caller requests it by sending a DTMF tone, otherwise switch to data/fax mode As you might see, the spoken greeting message is quite required to provoke a reaction of voice callers. Because there is no space yet in the modem's RAM preserved for storing a greeting message, the above method cannot be automated and done by the modem stand-alone. This makes it impossible for communications software - which has not been designed to do so - to distinguish between data and voice calls. (Anyway, for software like a FidoNet mailer that uses the FOSSIL serial driver, a tricky TSR utility exists to do the job - ask me, the author ;-)" N.B.: This is a new entry. As far as the Keeper of the ZyXEL FAQ knows, it is factually correct.
Subject: T.22 Are the specifications for converting voice files available? -------------------------------------------------------------------------------- Yes they are available. See VCNVT.C (or VCNVT.EXE) for conversion examples. also, the file format is described in VOICE.TXT. For decoding CELP data, the respective filename is "CELPC.*". Those archives could be obtained from several ftp servers and public mailbox systems.
Subject: T.23 Can speech be digitized/recorded and played back simultaneously? -------------------------------------------------------------------------------- Brent Mosbrook ( [ZyXEL USA] writes: "There are two DSP's in the modem right now.. one does the outgoing play, while the other handles incoming DTMF detection. It is theoretically possible to do what you describe, but I know of no plans to do so in this generation of hardware." Kolja Waschk (kawk@Yo.COM) writes: "It digitizes and analyzes the sum signal at any time when in Voice Mode so that DTMF tones and calling tones are recognized anytime (this results in the recognition of DTMF tones which are included in the voice to replay), but you cannot do both, replay voice from disk and record the incoming signal to your disk at the same time. (Imagine, using 2-bit ADPCM, this would require a data flow of totally more than 4800 cps without pauses between the bytes.)"
Subject: T.24A Can DTMF tones be recognized at any time during recording/ playback? -------------------------------------------------------------------------------- Kolja Waschk (kawk@Yo.COM) writes: "Yes. Detection of DTMF tones and calling tones was poor with earlier firmware versions, but became quite satisfying with firmware 6.11. Modems equipped with firmware versions below 6.10 have been able to detect DTMF tones _only_ while recording/replaying voice; newer firmware allows detection of DTMF and calling tones also while in command mode." Brent Mosbrook ( [ZyXEL USA] adds: "6.10a added the S39.6 register, which allows DTMF detection all the time."
Subject: T.24B Why is there a noise before a voice file is played through telco line ? -------------------------------------------------------------------------------- Kolja Waschk (kawk@Yo.COM) writes: "To make the DTMF detection more reliable, ZyXEL implemented an echo cancellation filter in the DTMF detection software in the Elite series. This filter requires a short probe to determine the channel parameters; it takes place only once before the first sound is to be played over a phone connection - thus the "noise". The result is a very reliable DTMF detection - my modem detects tones generated by the cheapest DTMF transmitters even while playing music. (There should be some S-register bit to disable this, but you'll have to look this up yourself, as it is not in my pre-release manual). In voice mode, one of the two DSPs is used solely for DTMF detection!" * Applicable to the Elite series only
Subject: T.25 What kind of problems exist with using voice software on Macintoshes? -------------------------------------------------------------------------------- Lars J Poulsen ( writes: It has been suggested that the newer firmware might use better compression, and thus work better on a slow machine/slow port. Can this be confirmed ? Brent Mosbrook ( [ZyXEL USA] replied: Only if the vendors decide to USE the re-sync feature that is provided. Brent Mosbrook ( [ZyXEL USA] added: In working with a couple vendors of MAC based voice answering systems, the speed of the machine, and the resource sharing settings can have a very direct, and pronounced effect on the quality of the recordings. Milton Sagen ( [Prometheus Products] writes: Unfortunately yes [there is the poor performance to be expected on an old, slow machine]. We informed ZyXEL that we didn't recommend running the software on 8 MHz 68000's until they implemented, what we refer to as, resyncing of the voice data. They have now done so in their 6.10 ROMs and the ball is now in our court. Hopefully we will get to it soon but until then the behavior you describe is what we expected to happen on machines such as the SE.
Subject: T.26 Why is there a slight hissing sound from the speaker? -------------------------------------------------------------------------------- Robert Wong ( and antekl ( remarked: Some modems will make a hissing noice coming from the modem's speaker. It's not very loud, yet loud enough to be heard in a quiet room by a person sitting nearby the modem. This sound is still heard, despite the ATM0, ATL0 and ATN0 register settings. Michael Schuster ( wrote: The early boards had three control resistors on the audio amp which were not quite the right value. As a result the speaker was never completely off. That was ages ago ... well before the Plus models were designed. On the older board you either replaced three 2.2K resistors with something higher (3.3K worked for me as I remember) or else stuff some paper toweling between the speaker and the case.
Subject: T.27 How does one make Caller ID (CID/CND) work correctly? -------------------------------------------------------------------------------- Caller ID or Caller Number Delivery is a *paid* service that *may* be available from the local phone company. One can *subscribe* to this service and get a ZyXEL modem to display the time, name and phone number of the calling party. To enable Caller ID detection by the ZyXEL, type in "ATS40.2=1" in a terminal program. This procedure was paraphrased from pages 12-5 and 12-6 of the ZyXEL User's Manual (Revision 2.1). [pages 12-3 and 12-4 in the on-line version] It should enable Caller ID detection. Should the above procedure be unsuccessful, then a hardware modification might be necessary. (c.f. T.26A)
Subject: T.27A What exactly is the hardware modification needed for CID/CND and EDR? -------------------------------------------------------------------------------- Brent Mosbrook ( [ZyXEL USA] writes: "All new ZyXEL modems have a hardware modification performed at the factory. A capacitor has been added to filter the Caller ID data. Current owners can have their modems upgraded by sending the modem back to ZyXEL, and we will install this capacitor for them. This might not be necessary, and is only recommended for people who live in an area with CND, and cannot get it to work. Any ZyXEL owner can call us and we will help them determine if they have the capacitor installed." Brent Mosbrook ( [ZyXEL USA] writes: EDR on non-US modems: It has come to our attention that EDR (included with 6.11a roms) does not work on modems bought outside the US or Canada. North American modems have a capacitor installed which is used to filter CID, and other tones received prior to the modem going off-hook. ZyXEL will not be referencing EDR capability on any "international" modems sold. Customers who wish to install this capacitor may do so at their own risk (local telco regulations may restrict performing this modification). Due to these possible restrictions, ZyXEL will not be offering a factory upgrade, but will help customers in identifying 1) whether or not they currently have the capacitor installed. 2) where the capacitor should be located. NOTE: DOING THIS MODIFICATION WILL VOID YOUR WARRANTY, AND MAY VOID THE LOCAL PTT APPROVAL. A .033 uF capacitor needs to be installed parallel to resistor R4 (100K ohms), which is located in different places according to the model, and revision level of your modem. A diagram showing the lastest revision levels is included to show the general area where R4 can be found. R4 is generally located near the relays (large yellow, brown or black boxes). The color code for R4 is brown-black-yellow-gold.(some locally approved models may have other values. Generally it is between 75K and 150K ohms.) The capacitor should be non-electrolytic, and rated at 100V or higher. (these are the latest rev. levels.. older models may differ significantly) 1496S/S+ modems: ---------------- RJ-11 RJ-45 --------------- --- --- ----- | RS-232 | | | | | | | --------------- --- --- ----- ------- |RELAY| ------- ------- o |RELAY| ! <-- R4 ------- o ------- |RELAY| ------- 1496E/E+ modems: ---------------- RJ-11 --------------- --- --- | RS-232 | | | | | --------------- --- --- ------- |RELAY| o ------- ! ------- o |RELAY| o ------- ! <-- R4 o 1496B/B+ modems: ---------------- |- ----------------------------------| | --| | | RJ-11 --| --| o | | RJ-11 R4 --> ! --| o | | | | -----------------------------------| |
Subject: T.27B What software modifications are needed? -------------------------------------------------------------------------------- If Caller ID detection is STILL not functional after the hardware modification, a possible though rarely used solution is to set the timing of certain registers. Robert McKeever ( writes: Way back in September, ZyXEL released a note (now disappeared off my drives) which described the use of the S45 and S46 registers to set timing. They (wrongly) assumed that the ringing on the GTD-5 exchanges was exactly 1.75s, following by 50ms silence, then data; for DMS-100 as a 2s - 3.5s ring interval, followed by 500ms of silence. The CallerID length depends on the amount of data the exchange transmits as its message. **********************------++++++++++++++++++ ^ ^ ^ | | | Ring Silence CallerID Data I quote from their message: << It is difficult for the modem to receive CallerID signals for both exchanges without configurable parameters. Two new parameters are implemented for this purpose, S45 and S46. They are called "guard time" and "silence interval", respectively. The silence interval is the consecutive silence that the modem should detect after ring on before CallerID signal to be processed. Distinctive ringing may be combined with CallerID, and therefore a guard time is needed for the modem to inhibit the silence detection. Registers S45 and S46 are in units of 20ms. Default setttings should be in the range of S45=100, S46=28 for DMS-100 (Bell, Northern), and possibly S45=87 and S46=3 for GTD-5 switches. >> The place this argument falls down, is on the GTD-5 switch, where they use "flash ringing". Flash ringing starts at any point in the ring cycle, which means you can get anywhere from 0.1s up to 2.0s of ringing current before the 50ms silent period followed by data from the central office switch. In any event, you now have the parameters for the critical registers for CallerID, for whatever good it may do you.
Subject: T.27C What else do if CID/CND and EDR still doesn't work? -------------------------------------------------------------------------------- Contact ZyXEL USA with the following information: 1. Make/Model of telco switch serving you. examples: AT&T 5ESS AT&T 1AESS Northern Telecom DMS-100/200 GTE GTD-5 2. Ring cadence, as measured by AT#B3 (this measures the ON/OFF times for incoming rings) 3. Rom revision level? c.f. T.1.A 4. Is there a capacitor on the R4 resistor? c.f. T.26A Based on the answers to the above questions, ZyXEL can recommend values for the registers. ALL of the questions need to be answered to provide a reasonable response.
Subject: T.28 What changes are needed for overseas calling? -------------------------------------------------------------------------------- Anees S. Munshi ( asks: "While making overseas calls to specfic countries, the current ZyXEL modems mistake the ringing tone for a busy signal and hangup. While this can be defeated by setting mode X3 or X1, it is nice to have busy tone detection on, and disable it only for specific phone numbers." Try ONE of the changes below to prevent the problem of false busy signals: . disable busy detection completely with AT X2. This is not a very good solution, as ALL busy signals are then ignored. . set Australian short-short ring detection on with S44.7=1. This may work for the country being called. . append a ;O (a capital "O") to the end of the phone number. e.g. ATDT 1234567;O Immediately after dialing the phone number, the modem goes into command mode and then it goes into an on-line state.
Subject: T.29 What modifications are needed to S/S+ models to get the eye pattern option? -------------------------------------------------------------------------------- This modification enables the 3 pins next to the power connector for the connection of an oscilliscope to view an eye pattern for line diagnostics. Lars J Poulsen ( wrote: "The eye pattern is a graphical tool for displaying certain internal parameters from the digital signal recovery in a V.32(bis) modem. A table of intermediate results is fed into a pair of digital-to-analog converter channels, which can be connected to the X Y Z inputs of an oscilloscope in X/Y mode. This displays a characteristic pattern of dots when the modem is trained." Note: these 2 chips are CMOS devices and are static sensitive. Use suitable caution. chip Number Part Number Manufacturer Description -------------------------------------------------------------------------- U11 AD7528JN (Analog Devices) 8-bit buffered DAC U12 TL072CP Texas Instruments 2 x FET op-amp Paul Cantrell ( called ZyXEL USA to modify his S/S+ modem to display the eye pattern. Apparently ZyXEL USA no longer does the modifications any more. The demand for this service was requested so infrequently that they don't have the traces on the new boards. ================================================================================ -- Robert Wong Jr. 1921 East 61st Avenue, Vancouver, B.C., Canada, V5P 2K2, (604) 322-6918 or Keeper of the ZyXEL FAQ and Head of the UBC-NeXT Users Group Standard disclaimers apply.

User Contributions:

Comment about this article, ask questions, or add new information about this topic:


Part1 - Part2 - Part3 - Part4 - Part5 - MultiPage

[ Usenet FAQs | Web FAQs | Documents | RFC Index ]

Send corrections/additions to the FAQ Maintainer: (Robert Wong Jr.)

Last Update March 27 2014 @ 02:11 PM