$Header: /usr/people/sam/fax/RCS/MODEMS,v 1.34 1994/07/03 22:46:46 sam Exp $Modem Bugs and Gotchas----------------------    Copyright (c) 1990, 1991, 1992, 1993, 1994 Sam Leffler    Copyright (c) 1991, 1992, 1993, 1994 Silicon Graphics, Inc.    Permission to use, copy, modify, distribute, and sell this software and     its documentation for any purpose is hereby granted without fee, provided    that (i) the above copyright notices and this permission notice appear in    all copies of the software and related documentation, and (ii) the names of    Sam Leffler and Silicon Graphics may not be used in any advertising or    publicity relating to the software without the specific, prior written    permission of Sam Leffler and Silicon Graphics.    THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND,     EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY     WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.      IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR    ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,    OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,    WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF     LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE     OF THIS SOFTWARE.This file contains information about modem bugs and gotchas that havebeen gleaned from experiences making the FlexFAX code work with themodems.  These problems are based either on my experiences or onexperiences of others that have worked with the software.  One shouldalways checked the version of the firmware listed.  Note also that if amodem is not listed here then I have NOT tried it.  This list should besorted in alphabetical order.Class 1 Modems--------------AT&T Paradyne		DataPort 14.4/FAX	C01.166.10o received HDLC frames do NOT include the FCS bytes (revs before 133)o carrier is sometimes dropped w/o notice during receive (rev 133)o the command "ATH+FCLASS=0;A" does not do the right thing because the  command parser does not parse the ";A"o the modem returns "OK" instead of "NO CARRIER" or "NO ANSWER" when a  dial attempt times out before carrier is establishedDigicom			Scout+			2A19/2931o +FMFR?, +FMDL?, and +FREV? all return "3" in some versions of firmwareo S17=2 can be used to force 1300 Hz CNG tones to be sent (the  register is not documented)o RTS/CTS is not honored while sending page data; software flow  control must be used (*F2).  This is fixed in rev 3507/3506 firmware  by adding a register S24 that can be used to control flow control  in facsimile mode: 0 means use XON/XOFF, 1 means use RTS/CTS, and  2 means use whatever is specified by *F.  Note however that S24  is not permanent; it is reset after each disconnect.  On power on  S24 is 0.  S24 is unchanged by &F.o receiving at 4800 baud v.27 does not work correctly; received  data is garbage		[fixed in firmware revision 3225/3310]o commands must not be sent to the modem too fast, no more than  every 50ms (or more) depending on what the modem is doingo the modem gets confused by receivers that assert a data  carrier before sending CED; a +FCERROR result is returned before  usually returning "NO CARRIER"; this can sometimes be overcome  by sending 1300 Hz CNG tones instead of the normal 1100 Hz tonesHayes			Optima 2400+Fax96	TR00-J260-001 XXXo receiving is unreliable; I was never able to get the receipt  of TCF to work correctly in the short time that I had the modem  (no data was delivered after establishing carrier before timeout)o see also below under Class 2Nuvo			Voyager 96424PFX	AF-C2500-E0o RTS/CTS is not honored; use software flow controlo factory configuration of &C1 causes problems; do "AT&C0&W" to set  DCD handling before running the servero beware of battery drainSupra			SupraFAX v.32bis	V1.200-H TR14-Jxxx-001o the +FAE command that can be used to enable auto-detect of calls from  data modems is only accepted in Class 0 (data mode); I've never been  able to get it to work correctly (when setup the modem is either unable  to establish carrier, or the modem locks up after notifying the host)o RTS/CTS is not honored while sending/receiving page data; use &K4 for  software (XON/XOFF) flow controlo see also below under Class 2Twincom			144/DF			V1.270 TR14-Jxxx-001o RTS/CTS is not honored while sending/receiving page data; use &K4 for  software (XON/XOFF) flow controlo see also below under Class 2USRobotics		 Sportster		Supervisor 4.1 (04/22/93)						DSP 10 (03/23/93)o timing problems have been observed with older firmware revisions;  if you have problems, be sure to verify the firmware revisiono when sending DCD is raised when carrier is first received, but it is  then dropped from the first HDLC receive until the point where the  initial training is sent (from that point on DCD is asserted); this  can be a problem because there is no way to override this behaviour  which means that the host must be capable of ignoring DCD for sending  to function correctlyo in testing the modem locked up during transmission to a Multi-Tech 1432BA  modem and failed to respond to the host dropping DTRClass 2 Modems--------------AT&T Paradyne		DataPort 14.4/FAX	C01.166.10o result strings for +FDCC=? and +FDIS=? are semantically incorrect;  ranges are returned as (a,b) instead of (a-b); e.g. (0,5) instead  of (0-5) for signalling rate; this causes problems in deducing the  true set of modem capabilitieso the modem sends the host ^S/^Q during page data transmission (+FDT)  even when RTS/CTS flow control is enabledo copy quality checking cannot be disabledo there is no support for transmission of 2D-encoded datao the modem was observed to enter a state where it repeatedly sent  EOP when commanded to send MPS (for AT+FET=0); power-cycling the  modem cleared this conditiono when entering Phase C, the modem does not appear to correctly drop  CTS before sending CONNECT to indicate that page data may be sent;  this can result in lost page datao the modem returns "OK" instead of "NO CARRIER" or "NO ANSWER" when a  dial attempt times out before carrier is establishedEverex			EverFax 24/96D		911027o zero-padding in the EOL codes of received facsimile data is often  not zero when the Phase B+D bit ordering is set to "direct"; a  workaround is to use +FBOR=2 and do bit reversal in the hostHayes			Optima 2400+Fax96	TR00-J260-001 XXXo many commands (e.g. ATZ) generate annoying clicks & pops from  the speakero using '@' in the dialing string causes the modem to return  "NO ANSWER" when calling many modemso the modem does not do a good job of holding reliable high speed  carrier--when sending and receiving, data is frequently corrupted  at both 9600 and 7200 baud (the phone line did not appear  to be the reason as other modems worked fine in back-to-back  testing)Multi-Tech		MT1432BA		0307o there are problems communicating with Sharp model 6200 fax machines;  this is reportedly fixed in rev 0309 firmwareo the EC (error correction) subparameter reported in +FDIS: result  strings can contain invalid values (2)Practical Peripherals	PM14400FXMT		2.17o defaulted subparameters in +FDIS and +FDCC commands are wrongly  treated as zeroo +FDIS commands to set session parameters after establishing a  connection with a remote machine are accepted but ignored; this  makes it impossible to select/change data format (1D vs 2D encoding)  and vertical resolution (98lpi vs 196lpi); to workaround the problem  use the Class2DDISCmd configuration parameterSupra			SupraFAX v.32bis	V1.200-H TR14-Jxxx-001o changing DCD handling can cause the modem to drop DSR; if done  during initialization this can cause the fax server to get confused;  be sure that the setting loaded from NVRAM on reset agrees with  the value specified in the config file (&C1 by default); one  possible way of doing this is to specify &F2 for the ModemResetCmds  parametero the line counts in the +FPTS result code during a reception are  total nonsense; the only way to deduce the number of lines in a  received page of data is to parse the data on the hosto facsimile reception is locked at 19200 baudo adaptive answer is not reliableo the training algorithm can loop forever; client software must  timeout +FDR requestso RTS/CTS is not honored while sending/receiving page data; use &K4 for  software (XON/XOFF) flow controlo the firmware often responds incorrectly to an EOM post-page message;  the modem has been observed to drop carrier and/or respond with an  incorrect HDLC message[Firmware rev V1.80-02 TR14-Jxxx-001 is a significant improvement over previous firmware; it is highly recommended that you upgrade your modem if you do not have firmware at or near that rev level.]Telebit			T3000A			Version LA7.02o when HDLC frame tracing is enabled, the modem sometimes does not  send the +FCON status message to the hosto when carrier is dropped during the training phase that follows a  +FDT command, the modem sometimes violates the Class 2 spec by  returning "NO CARRIER" and not a +FHNG status stringTwincom			144/DF			V1.270 TR14-Jxxx-001o changing DCD handling can cause the modem to drop DSR; if done  during initialization this can cause the fax server to get confused;  be sure that the setting loaded from NVRAM on reset agrees with  the value specified in the config file (&C1 by default);o instead of the normal &D3 setup string for RC144AC-based modems,  &D2 should be used (note that this configuration must be done  manually as faxaddmodem is incapable of distinguishing between  RC144AC-based modems)o the line counts in the +FPTS result code during a reception are  total nonsense; the only way to deduce the number of lines in a  received page of data is to parse the data on the hosto the modem has frequently been observed to just lockup during message  receive (i.e. +FDR); it dropped DCD to the host but did not return  <DLE><ETX> and/or a +FHNG codeo in testing the modem locked up during transmission to a Multi-Tech 1432BA  modem and failed to respond to the host dropping DTRUcom A/S		Traveller 96		SSX996/1.32, 120691,SSCo remote TSI strings are returned without matching quote marks;  as a result the current software truncates the TSI strings to be nullo AT+FCLASS=2 causes the host-modem interface to be locked at 19.2KB  irrespective of the modem configuration and baud rate in use prior  to the commandZero One Networking	ZyXEL 1496E		U1496E  V 5.02 Mo +FMDL? and +FREV? return the same string, the concatentation of  the modem model and the firmware revision.o some prom revisions do not include a trailing "OK" in response to  +FDCC=?o DC2 must be sent to the modem to trigger the transfer of Phase C  data from the modem to the host after a +FDR command; this reflects  revision 2388-B of the Class 2 spec and is different from the DC1  required by 2388-A (and accepted by most modems)+ the modem advertises that it supports the 2DMR data format, but it  does not; this "advertisement" is both in its result string for a  +FDCC=? query and in the DIS/DCS sent to clients+ sending 2DMR data to the modem can cause it to lock up leaving CTS  low to the host; some versions of firmware also send an infinite  stream of trash to the remote side when this condition occurso in some prom revisions the result string from a +FDCC=? query does  not conform to any syntax listed in either 2388-B or 2388-A;  furthermore, it requires a context sensitive parser!+ +FDIS commands to set session parameters after establishing a  connection with a remote machine are accepted but ignored; this  makes it impossible to select/change data format (1D vs 2D encoding)  and vertical resolution (98lpi vs 196lpi); since it is not in general  feasible to set all session parameters before dialing the telephone,  this problem makes it possible only to support the minimum set of  Group 3 capabilities (1D data, 98 lpi)o sending non-Class 2 commands to the modem after establishing a  connection often causes the modem to drop carrier; for example,  ATM0 before a +FDR command will do this;o the line counts in the +FPTS result code during a reception are  total nonsense; the only way to deduce the number of lines in a  received page of data is to parse the data on the hosto in later versions (5.05 for example) the syntax of the +FPTS:  result code violates 2388-A and/or 2388-Bo there is no way to abort a session (i.e. the +FK command is not  recognized)+ when sending, the modem appears to immediately drop DCD when it  loses carrier; this usually occurs after a final +FPTS is sent  to the host, but before the requisite OK and and/or +FHNG strings;  this action appears to be independent of whether or not DCD is  configured to follow carrier (i.e. &C0 or &C1)+ when receiving with a negotiated 14400 signalling rate, the +FDCS:  status string indicates a 9600 baud signalling rate (br=3)+ the reception of multiple documents appears to cause the modem to  hangup (i.e. an EOM post page message causes the modem to hangup)+ the modem sometimes sends received data to the host with the  wrong bit ordero the scheme used to do adaptive-answer asserts a data carrier before  falling back to a fax carrier;  this can confuse a few fax modems and  make it impossible to receive facsimile without disabling adaptive  answer (+FAA=0)o AT+FLID? returns OK but not the current value of the local identifier.o the modem sends the host ^S/^Q during page data transmission (+FDT)  even when RTS/CTS flow control is enabled+ = This problem is known to be corrected in firmware revision 6.01.Class 2.0 Modems----------------USRobotics		 Courier		Supervisor 505-5.1 (03/14/94)						DSP 11.1 (12/08/93)o previous Supervisor firmware revs were known to not function correctly;  in particular, rev 5.1 (12/10/93)o certain firmware revisions incorrectly interpret the signalling rate  session parameter in +FIS and +FCC commands; this causes the modem to  attempt to negotiate session communication at 2400 bpsZero One Networking	ZyXEL 1496E		U1496E  V 6.12 Mo no known problems