class2.txt

使用efax的fax工具程序

                   SUPRA TECHNICAL SUPPORT BULLETIN 
               CLASS 2 FAX COMMANDS FOR SUPRA FAXMODEMS 
                              6/19/92

Supra Corporation
7101 Supra Drive SW, Albany, OR  97321
General [phone] / Sales [phone] / Fax [phone]
Supra Tech Support  [phone]  8:00am - 5:00pm PST, M-F

Supra BBS........[phone]  24 Hours
CompuServe.......76004,565
BIX..............SupraCorp
America Online...SupraCorp2
GEnie............SupraTech
AppleLink........D2456
UseNet [e-mail]
            .....supra![e-mail]

SUPRA's DISCLAIMER:
   The following information has been taken from Rockwell's RC144AC 
manual. It has not been taken from the CCITT Class 2 documentation, 
which is copyrighted by the CCITT.  This information is provided for 
educational purposes only.  To fully understand this information 
requires a through knowledge of the T.4 fax image and the T.30 fax 
session protocol standards.  Due to the nature of this information, 
Supra's engineers and technical support can not and will not provide any 
help or support on this information.  While a majority of this 
information is correct, neither Supra nor Rockwell implies or warranties 
that the SupraFaxModem will work exactly as documented here. This 
information is based on an early draft of Class 2, which has undergone 
further revisions and changes by the CCITT TR29.2 committee.  We 
STRONGLY urge anyone attempting to develop fax software to get the 
required documentation from Global Engineering or the TIA.

SHORT HISTORY OF CLASS 1 AND 2
  In 1988 the CCITT TR29.2 committee accepted the Class 1 standard for 
communication between fax software and fax modems.  The committee also 
voted on, but did not accept for various technical reasons, the Class 2 
standard.  A year later, they had slightly revised the standard but 
again did not accept it.  Software and hardware manufactures decided to 
unofficially adopt this standard until the TR29.2 committee could 
develop an acceptable standard.  Since so many companies have used the 
unoffical standard, the TR29.2 committee has designated that when the 
standard is offically adopted it will be known as Class 2.0.  Over the 
last year or so, the TR29.2 committee has voted on several revisions to 
the Class 2 standard.  Their last vote was early May '92.  A no vote for 
technical reasons was entered.  The TR29.2 committee is now reviewing 
the technical issues that were raised.  At this time, Supra has not 
heard of a projected date for the next ballot.

WHAT IS THE DIFFERENCE BETWEEN CLASS 1 AND 2
  Class 1 fax software handles all of the T.4 fax image and T.30 session 
protocol information and timming.  Thus, the ability to communicate 
properly with various fax machines is more a function of the software 
than the fax modem.  Class 2 fax software generates a T.4  fax page 
image and sends it to the fax modem a page at a time.  The fax modem 
then handles the T.30 session protocol information and timming.  This 
relieves the computer's cpu from some work.  The ability to communicate 
properly with various fax machines is more a function of the fax modem 
than the software.  However, to further complicate matters, class 2 fax 
software can issue Class 1 commands and take over some of the duties of 
the Class 2 fax modem.  

  When customers have a problem communicating correctly with a fax 
machine/modem, it can be very difficult to determine which is at fault,
 the software or the hardware.  Supra has collected numerous Class 1 and 
2 fax software for a variety of different computers.  When we receive a 
report of a problem, we use these programs to determine if it is a 
software or hardware problem.  If it is a hardware problem, we notify 
Rockwell, otherwise we notify the software company.

BUG REPORTS
  Supra is dedicated to making the best product for the best price.  If 
you feel that you have found a bug, please fax or send a letter to the 
attention of:

   SUPRA V32/BIS FAX BUG

Please fully describe the 'bug' (specific steps to generate it, phone 
numbers to call, make and model of fax/modem, rev of our ROM (from I3 
command) ), why you believe that it is a bug, what specific section of 
Class 2 applies to this bug and how you would like the bug to be fixed.  
Please remember that there are issues that have not been addressed or 
settled by the TR29.2 committee in the Class 2 specifications. (i.e. how 
the DCD and DTR lines are handled while in fax mode.)


WHERE TO GET OFFICIAL FAX DOCUMENTATION

  Telecommunications Industry Association
  1722 Eye St. NW
  Suite 440
  Washington, DC  20006

You need to ask for:

    Class 1 documentation - EIA/TIA-578
    Class 2 documentation - Electronic Industries Association and 
Telecommunications Industry Association TIA Project Number 2388, 
Asynchronous Facsimile DCE Control Standard, Service Class2, TR-29.2 
Committee Letter Ballot

  Global Engineering Documents                     
  2805 McGaw Ave
  Irvin, CA  92713 
  800-854-7179
  714-261-1455
  714-261-7892 (Fax)     

You need to ask for:

    EIA/TIA-578 - Class 1 documentation
    EIA/TIA-592 - Class 2 documentation
    CCITT v7.3  - T.1 - T.90 standards, includes T.4 & T.30

(The cost for the above docs will run close to $200.  But Global will 
also update you on any changes or additions to those standards you 
purchase.)

Global Engineering will not have the Class 2 documentation until approx. 
a month after the TR29.2 committee accepts it.  Most of those companies 
which have developed Class 2 fax software either sit on the TR29.2 
committee or know someone who does.  It may be possible to receive the 
documentation from the TIA if you present a credible proposal.  Supra 
has no knowledge of what this proposal should consist of or who you need 
to talk to.


7.1  COMMAND SYNTAX AND GUIDELINES

7.1.1 DTE COMMANDS

The ISO 646 character set (T.50 International Alphabet 5, American 
Standard Code for Information Interchange) is used for the issuance of 
commands and responses.  Only the low-order 7 bits of each character are 
used for commands or parameters; the high order bit is ignored.  Upper 
case characters are equivalent to lower case characters.

For Phase C data transmission or reception, all 8 bits are needed.

DTE COMMAND LINES

A command line is a string of characters sent from a DTE to the DCE 
while the DCE is in a command state.  Command lines have a prefix, a 
body, and a terminator.  The prefix consists of the ASCII characters 
'AT' (065, 084) or 'at' (097, 116).  The body is a string of commands 
restricted to printable ASCII characters, (032-126).  Space characters 
(ASCII 032) and control characters other than CR (013) and BS (010) in 
the command string are ignored.  The default terminator is the ASCII 
<CR> character.  Characters that precede the AT prefix are ignored.

BSIC COMMAND SYNTAX

Characters within the command line are parsed as commands with 
associated parameter values.  The basic commands consist of single ASCII 
characters, or single characters preceded by a prefix character (e.g., 
'&'), followed by a decimal parameter.

Missing decimal parameters are evaluated as 0.

EXTENDED COMMAND SYNTAX

The facsimile commands use extended syntax.  They are preceded by the 
'+F' characters, and they are terminated by the semicolon ';' character 
(059) or by the <CR> that terminated the command line.

         AT+FAA=0         ;+FCR 1 <CR>

This command instructs the DCE to answer automatically a data or fax 
call and also enables reception.

         AT+FCLASS=0 <CR>      for data mode
         AT+FCLASS=1 <CR>      for Service Class 1 Fax
         AT+FCLASS=2 <CR>      for Service Class 2 Fax

In Class 2, the DCE makes and terminates calls, manages the 
communication session and negotiates (T.30 protocol) and transports the 
image date to DTE.  The T.4 protocol management of image data, etc. is 
done by DTE.

The response to 
         
         AT+FCLASS=0<CR>       in Data Mode

or

        AT+FCLASS=2<CR>       in Service Class 2 Fax
         
is
       OK

The service class may be set by the DTE from the choices available using 
the '+FCLASS=<VALUE>' command.

GENERAL RULES

1.  +Fnnn commands must be entered completely otherwise an 
    ERROR response is sent.

2.  All response messages are preceded and followed by <CR><LF>. 
    Multiple response commands, e.g., +FDIS:+FCSI: and +FDCS, will 
    therefore appear to a have a blank line between them.

3.  Fax Class 2 commands can be separated by the ";" character.  The ";" 
    can be omitted if desired.  Note that non-data commands cannot be 
    separated by ";" which is allowed as a dial modifier.

4.  All class 2 commands are assumed to be the final command on a 
    command line.  Additional characters will be ignored.

5.  An ERROR message will be generated if any of the following 
    conditions:

      a.  A class 1 command is received while in Class 2.

      b.  A Class 2 command is received while in Class 1.

      c.  A Class 1 or Class 2 action command is received while in data 
          modem mode

      d.  A Class 2 read-only parameter is given the "=" form of a +F 
          command (e.g., AT+FAXERR=5).

      e.  A class 2 action command is given the inappropriate "=" or 
          "=?" (e.g., AT+FDR=?).

7.1.2 SERIAL PORT SPEED AND FLOW CONTROL

During fax mode, the DTE-DCE port speed is 19200 bps.

The DCE provides a speed buffer of 1024 bytes and provides DC1/DC3 
(XON/XOFF) or RTS/CTS method of controlling the data into the buffer.  
This flow control is controlled by AT&K3 or AT&K4 command.

This method of data flow control is available only for DTE to DCE 
direction of data.  There is no provision for data flow control from DCE 
to DTE.

DATA STREAM TERMINATION

The DCE exchanges streams of data with the DTE while executing data 
transfer commands.  These use data stream termination described in 
Section 3.2/ISO 2111.

The ASCII <DLE> character (016) is used as a special character to shield 
special characters.  The <DLE><ETX> character pair (<106><003>) is used 
to mark the end of a stream.  The following patterns are used:

   any data....<DLE><ETX>       end of stream
   any data....<DLE><DLE>       single <DLE> in data
   any data....<DLE><any byte>  delete <DLE><any byte>

DTE to DCE STREAMS

The DCE filters the data stream from the DTE, and removes all character 
pairs beginning with <DLE>.  The DCE recognizes <DLE><ETX> as the stream 
terminator.  The DCE recognizes <DLE><DLE> and reinserts a single <DLE> 
in its place.

The DTE must filter stream data to the DCE, and insert extra <DLE> 
characters ahead of data.

DCE TO DTE STREAMS

The DTE must filter the data stream from the DCE, and remove all 
character pairs beginning with <DLE>.  The DTE must recognize <DLE><ETX> 
as the stream terminator.  The DTE must recognize <DLE><DLE> and 
reinsert a single <DLE> in its place.

The DCE filters stream data to the DTE, and inserts extra <DLE> 
characters ahead of data.

7.1.3  AUTO ANSWER

The DCE can answer as a data DCE or as a fax DCE.  It can answer the 
call adaptively, i.e. it can determine whether call is 'data' or 'fax'.  
The +FAA parameter controls this feature.

     AT+FAA=1           ; Auto answer as a facsimile or a
                        ; data modem depending on call

     CONNECT xxx        ; DCE status response if data call

     +FCON              ; DCE status response if fax call

7.1.4  IDENTIFICATION OF T.30 OPTIONS

Group 3 devices negotiate session parameters in DIS, DCS and DTC frames. 
 These parameters are defined in table 8.2.

7.1.5  SESSION STATUS REPORTING

The DCE provides reports to the DTE on the status of a session.  The DCE 
provides following status reports:

1.  Connection and hang up status:

        +FCON

        +FHNG:<0-255>

2.  Requested DIS session parameters +FDIS:<string> reports remote 
    facsimile capabilities.

        Syntax:+FDIS:VR, BR, WD, LN, DF, EC, BF, ST

3.  +FDCS:<string> reports the negotiated parameters

4.  Phase C prompts:

        XON, XOFF, DC2

5.  Phase C base status reports: depending upon copy quality and related 
    end-of page status:
 
        +FPTS:<1-5>

7.1.6  PROCEDURE INTERRRUPT NEGOTIATION

CCITT allows a station to request a procedure interruption at the end of 
a page.  This request is passed between stations by the PIP, PIN, and 
PRI-Q messages.


TABLE 7-1. FAX CLASS 2 COMMANDS
-----------------------------------------------------------
|   Command        Function                               |
|---------------------------------------------------------|
|   SERVICE CLASS ID                                      |
|---------------------------------------------------------|
|   +FCLASS=       Service Class                          |
|---------------------------------------------------------|
|   CLASS 2 ACTION COMMANDS                               |
|---------------------------------------------------------|