Facsimile and static presentation processing – Facsimile – Facsimile system interface
Reexamination Certificate
1999-03-24
2002-08-27
Williams, Kimberly A. (Department: 2622)
Facsimile and static presentation processing
Facsimile
Facsimile system interface
C379S100170
Reexamination Certificate
active
06441926
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a facsimile machine and a TCF (Training Check Field) reception method for a facsimile machine, and in particular, to a facsimile machine and a TCF reception method for a facsimile machine which utilize EIA 578 facsimile control commands (AT commands) and which operate according to timing defined in ITU-T T.30.
DESCRIPTION OF THE PRIOR ART
Among various types of information communication means provided today, information communication by facsimile has a strong point in that text, characters, images or whatever on a sheet can be transmitted easily and directly, and facsimile machines have come into wide use in many countries.
A facsimile machine generally comprises a fax/modem section as the interface of the facsimile machine to a public network circuit such as a public switched telephone network and a computer unit etc. for executing processing of data (received data or data to be transmitted) and outputting AT commands to the fax/modem section.
In the following, an example of a conventional facsimile machine and a conventional TCF reception method for a facsimile machine will be described referring to FIG.
1
through FIG.
4
. Incidentally, FIG.
2
through
FIG. 4
will also be used later for explaining a facsimile machine and a TCF reception method for a facsimile machine in accordance with the present invention.
Referring to
FIG. 2
, the conventional facsimile machine is composed of a computer unit
1
which operates according to control of a program and outputs AT commands, and a fax/modem
2
which is connected to a communication line. The fax/modem
2
includes an AT command execution analysis section
21
and a signal processing section
22
. The AT command execution analysis section
21
and the signal processing section
22
are realized by, for example, one or more microprocessor units which are composed of one or more CPUs (Central Processing Units), ROM (Read Only Memory), RAM (Random Access Memory), etc.
Incidentally, while the computer unit
1
and the fax/modem
2
are provided apart in
FIG. 2
, of course, the computer unit
1
and the fax/modem
2
can also be installed in one body as an integral-type facsimile machine. In addition, while the hardware fax/modem
2
is employed as the fax/modem section of the facsimile machine in
FIG. 2
, the fax/modem section is not limited to such a hardware fax/modem section and it is also possible to realize the fax/modem
2
by software that is installed on a computer (for example, the computer unit
1
) and executed by a CPU of the computer.
In the following, the operation of the components of the conventional facsimile machine shown in
FIG. 2
will be explained.
The computer unit
1
sends AT commands to the fax/modem
2
and thereby instructs the fax/modem
2
to execute sending or reception of a fax. The AT command execution analysis section
21
in the fax/modem
2
analyzes an AT commands sent from the computer unit
1
and executes the AT commands. The signal processing section
22
executes transmission of signals to the communication line or reception of signals from the communication line.
FIG. 1
is a schematic diagram showing changes of states of the fax/modem section in the conventional facsimile machine. Referring to
FIG. 1
, the internal state of the conventional fax/modem section can roughly be classified into an AT command standby state (state #1) in which the fax/modem section waits for supply of an AT command from the computer unit
1
and an AT command execution state (state #2) in which the fax/modem section executes an AT command. For example, the conventional fax/modem section is in the state #2 when the fax/modem section is receiving a DCS (Digital Command Signal) via the communication line, and changes into the state #1 (AT command standby state) after finishing reception of the DCS. After receiving an AT command (which instructs the fax/modem section to receive a TCF) from the computer unit
1
, the conventional fax/modem section changes into the state #2 and executes a TCF reception process.
As described above, the internal state of the conventional fax/modem section includes the state #1 and the state #2, and the fax/modem section is in the state #1 or in the state #2 at a moment.
In the following, the operation for sending and receiving signals employed in the conventional facsimile machine and the conventional TCF reception method will be described referring to figures.
FIG. 3
is a timing chart showing an example of signals which are sent via the communication line and received by the fax/modem
2
. The signals shown in
FIG. 3
are signals according to ITU-T T.30, including a TSI (Terminal System Identifier)
201
, a DCS (Digital Command Signal)
203
and a TCF (Training Check Field)
205
. The above acronyms will be used in the same meanings throughout the document and figures.
When the signals shown in
FIG. 3
are received by the fax/modem
2
, commands and responses shown in
FIG. 4
are communicated between the computer unit
1
and the fax/modem
2
.
FIG. 4
is a schematic diagram showing an example of input AT commands and response AT commands which are received and transmitted by the fax/modem
2
.
Referring to
FIG.4
, the AT command “AT+FRH=3” (command
301
) is a command for instructing the fax/modem
2
to receive an HDLC frame, and the AT command “AT+FRM=96” (command
303
) is a command for instructing the fax/modem
2
to receive a TCF. Here, the HDLC frame is a frame according to HDLC (High Level Data Link Control Procedure).
In the example shown in
FIG. 2
, the AT commands sent from the computer unit
1
are received and accepted by the AT command execution analysis section
21
of the fax/modem
2
. When the signal processing section
22
of the fax/modem
2
detected a carrier of the HDLC frame, the AT command execution analysis section
21
sends back a command
305
which means “CONNECT” to the computer unit
1
as a response to the command
301
. After the signal processing section
22
received the HDLC frame, the AT command execution analysis section
21
sends the HDLC frame to the computer unit
1
. When the signal processing section
22
detected end of data, the AT command execution analysis section
21
sends a command
307
which means “OK” to the computer unit
1
. When the signal processing section
22
detected a carrier of the TCF, the AT command execution analysis section
21
sends back a command
309
which means “CONNECT ” to the computer unit
1
as a response to the command
303
. After the signal processing section
22
received the TCF, the AT command execution analysis section
21
sends the TCF to the computer unit
1
. When the signal processing section
22
detected end of data, the AT command execution analysis section
21
sends a command
311
which means “NO CARRIER” to the computer unit
1
.
As described above, in the conventional facsimile machine and the conventional TCF reception method for a facsimile machine, the fax/modem
2
is supposed to execute transmission of signals to the communication line and reception of signals from the communication line correctly, by communicating AT commands with the computer unit
1
.
However, there exist some types of facsimile machines whose switching time between the HDLC frame and the TCF (i.e. time interval between finishing sending the HDLC frame and starting sending the TCF) is almost the same as the minimum interval which is allowed in the ITU-T T.30.
In the case where such a facsimile machine sends the above signals to the conventional facsimile machine which employs the conventional TCF reception method (i.e. which operates as has been explained referring to FIG.
4
), the conventional facsimile machine can not always establish communication with the facsimile machine, since the time interval is not enough.
Referring again to
FIG. 4
, the command
307
indicating a response “OK” to the command
301
(“AF+FRH=3”: requesting reception of an HDLC frame) is tr
Dickstein , Shapiro, Morin & Oshinsky, LLP
NEC Corp.
Williams Kimberly A.
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