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BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates in general to the field of data processing
systems and in particular to the field of data communication systems.
Still more particularly, the present invention relates to a method and
system for automatically determining a data communication device type and
a transmission speed associated with the data communication device type.
2. Description of the Related Art
Electronic communication is increasingly common in the world today. For
example, messages or documents may be transmitted between parties
separated by great geographic distances utilizing modems, facsimile or
voice communication systems.
Those skilled in the art will recognize that a modem is used to convert
digital bit stream into analog signals that are sent over telephone or
other transmission lines to a second modem. The second modem receives the
analog signals and reconverts the analog signals back to a digital bit
stream. The specific techniques used to encode the digital bit stream into
analog signals are called modulation protocols. The various modulation
protocols define the exact method of encoding and the data transmission
speed.
Transmission speeds vary depending on which type of modem is used. For
example, modems can transmit at 9600 bits per second (bps), 2400 bps, 1200
bps or 300 bps. The modulation protocol also identifies whether the modem
utilizes frequency-shift keying (FSK) or phase-shift keying (PSK) to
encode the data. As known in the art, under FSK the transmitted signal
shifts back and forth between two frequencies: one representing a one and
the other representing a zero. PSK utilizes shifts in phase to signal ones
and zeros.
For modems to be able to transfer data, the modulation protocol of one
modem must coincide with the modulation protocol of the second modem.
Those skilled in the art will recognize that modems can negotiate certain
features, such as error control, data compression, and transmission speed.
One method used to negotiate these features is for a modem to first
attempt to establish a connection at selected features, and if
unsuccessful, to fall back to alternative features.
One feature that is also negotiable is FSK or PSK data encoding procedures.
As known in the art, negotiation for data encoding can occur when a
separate set of transmit and receive hardware for each supported modem
type is provided. The negotiation process is accomplished by connecting
each separate set of transmit and receive hardware to the transmission
line. Once the negotiation process is successfully completed, only the
transmit and receive hardware for the specified modem type remains coupled
to the transmission line. All the other separate sets of transmit and
receive hardware sits idle for the duration of the data communications.
This can become costly in terms of hardware requirements, power
requirements, and physical space requirements.
Therefore, it should be obvious that a need exists for a method and system
for establishing data communications with modems which minimizes the need
to duplicate communication hardware.
SUMMARY OF THE INVENTION
It is therefore one object of the present invention to provide a method and
system for establishing data communications between two modems utilizing
common hardware.
It is another object of the present invention to provide a method and
system for automatically determining a data communication device type and
transmission speed associated with a particular data communication device
type.
It is yet another object of the present invention to provide a method and
system for establishing data communications between a first data
communication device and a second data communication device at an optimal
transmission speed.
The foregoing objects are achieved as is now described. An incoming
communication is detected on a transmission line, and transmit and receive
hardware are connected to the transmission line. Next, a sequence of
different signals in either a first communication protocol or a second
communication protocol are transmitted from a first data communication
device via the transmission line. The transmission line is then monitored
for a response signal from a second data communication device. The
response signal is initiated from the second data communication device in
response to receipt of a particular signal within the transmitted sequence
of different signals. Utilizing the relationship between the response
signal and the transmitted sequence of different signals, a data
communication device type and transmission speed are determined, and data
communications may then be established between the first data
communication device and the second data communication device at an
optimal transmission speed.
BRIEF DESCRIPTION OF THE DRAWING
The novel features believed characteristic of the invention are set forth
in the appended claims. The invention itself however, as well as a
preferred mode of use, further objects and advantages thereof, will best
be understood by reference to the following detailed description of an
illustrative embodiment when read in conjunction with the accompanying
drawings, wherein:
FIG. 1 is a pictorial representation of a data processing system which may
be utilized to implement the method and system of the present invention.
FIGS. 2a-2f are high level flow charts depicting the automatic
determination of a data communication device type and the transmission
speed associated with the data communication device type in accordance
with the method and system of the present invention.
FIG. 3 is a pictorial representation of a data communications system which
may be utilized to implement the method and system of the present
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
With reference now to the figures and in particular with reference to FIG.
1, there is depicted a pictorial representation of a data processing
system 10 which may be utilized to implement the method and system of the
present invention. As may be seen, data processing system 10 may include a
plurality of computers 14 which may be connected together in a local area
network 16. Of course, those skilled in the art will appreciate that a
plurality of intelligent work stations coupled to a host processor may be
utilized to implement such network.
As is common in such data processing systems, each individual computer may
be coupled to a storage device 18 and/or a printer/output device 20. One
or more such storage devices 18 may be utilized, in accordance with the
method of the present invention, to store the various data objects or
documents which may be periodically accessed and processed by a used
within data processing system 10, in accordance with the method and system
of the present invention. In a manner well known in the prior art, each
such data processing procedure or document may be stored within a storage
device 18, which may be associated with a resource manager or library
service, which is responsible for maintaining and updating all resource
objects associated therewith.
Still referring to FIG. 1, it may be seen that data processing system 10
may communicate with another system 12 which may include a second data
processing system, via electronic delivery utilizing a data communications
system 22, or by physical delivery using a post office 24. System 12 may
also receive messages via various data communication channels 36. As
utilized herein, the term data communication channel shall include various
electronic distribution systems such as telephone lines, a dedicated
facsimile line, and radio signals and shall also include various physical
delivery systems such as a postal letter carrier or messenger service. A
message may be characterized in various distribution media. As utilized
herein, the term distribution media shall include such data communication
devices as facsimile 28, telephone modem 30, voice mail 32, electronic
mail (e-mail) 34, or letter 26.
Now referring to FIGS. 2a-2f, there is illustrated high level flow charts
depicting a method for automatically determining a data communication
device type and the transmission speed associated with the data
communication device type in accordance with the method and system of the
present invention. An incoming communication is detected on a transmission
line, and transmit and receive hardware are connected to the transmission
line. Referring initially to FIGS. 2a and 2b, the process begins at block
38 and thereafter passes to block 40 which illustrates the initialization
of the method. A global timer is set at a predetermined value, a Signal 1
transmission is initiated, and a selected Transmit Loop Timer 1 is set. In
the preferred embodiment, the system and method of the present invention
is utilized for two modems attempting to transfer data, and the global
timer is set for 5,000 milliseconds (ms), Signal 1 is silence and Transmit
Loop Timer 1 is set for 1850 ms. The process then passes to block 42,
which depicts execution of subroutine 1. In the preferred embodiment,
communications are attempted by scanning for the most commonly used modems
first. Additionally, precautions are taken to preclude confusion between
the various types of modems.
Subroutine 1 is shown in FIG. 2c, and begins at block 44. Block 46
illustrates setting a receiver to scan for a 390 Hertz (Hz) tone and
setting the receiver timer for 140 ms. The process then passes to block
48, which depicts a determination of whether or not a 390 Hz response tone
is received. If a 390 Hz response tone is received, a particular data
communication device type and transmission speed are determined and data
communications are established, as shown in block 50.
If a 390 Hz response tone is not received, a determination is made in block
52 as to whether or not the Transmit Loop Timer is timed out. If it is
timed out, the process passes to block 54 where subroutine 1 returns to
the main program. If the Transmit Loop Timer is not timed out, another
determination is made as to whether or not the receiver timer is timed
out, as shown in block 56.
If a determination is made that the receiver timer is not timed out, the
process passes to block 58, which illustrates a determination of whether
or not the global timer set during initialization (see FIG. 2a, block 40)
is timed out. If the global timer is timed out, data communications have
not been established and block 60 shows an error code is posted and the
transmission line is disconnected. If the global timer is not timed out,
the process returns to block 48 to continue scanning for a 390 Hz tone.
Referring again to block 56, if a determination is made that the receiver
timer is timed out, the process passes to block 62 which depicts setting
the receiver to scan for a 980 Hz response tone and setting the receiver
timer for 60 ms. Block 64 illustrates a determination of whether or not a
response tone of 980 Hz is received. If a response tone is received, a
particular data communication device type and transmission speed are
determined and data communications are established, as shown in block 66.
If a determination is made that a response tone of 980 Hz is not received,
the process passes to block 68 where a determination is made as to whether
or not the Transmit Loop Timer is timed out. If the Transmit Loop Timer is
timed out, the process jumps to block 74, which illustrates subroutine 1
returning to the main program.
Referring again to block 68, if a determination is made that the Transmit
Loop Timer is not timed out, the process passes to block 70 which depicts
a determination of whether or not the receiver timer is timed out. If the
receiver timer is not timed out, the process continues at block 72, which
illustrates a determination of whether or not the global timer is timed
out.
If the global timer is timed out, data communications have not been
established and the process passes to block 60 which shows an error code
is posted and the transmission line is disconnected. If the global timer
is not timed out, the process returns to block 64 to continue scanning for
a 980 Hz tone. Finally, referring again to block 70, if a determination is
made that the receiver timer is timed out, subroutine 1 returns to the
main program, as illustrated in block 74.
Thus, in the preferred embodiment, subroutine 1 is utilized to detect FSK
configured modems. Modems detected during this call to subroutine 1 are
modems which do not require Consultative Committee for International
Telephone and Telegraph (CCITT) V.25 auto-answer protocol and which
transmit their starting signal as soon as they are connected to the
transmission line, regardless of whether Signal 1 is transmitted or not.
Calling subroutine 1 at this point in the process speeds up detection of
modems which transmit their starting signal as soon as the modems are
connected to a transmission line. Signal 1 is a required part of the CCITT
V.25 auto-answer protocol and is transmitted at this point in the process
for the benefit of modems that require it.
Referring again to FIG. 2a, block 76 illustrates a determination of whether
or not a response tone was received during execution of subroutine 1,
shown in FIG. 2b. If a response was received, data communications are
established as shown in block 78. If a response was not received, the
process continues at block 80 which depicts the initiation of a
transmission of Signal 2 and setting a selected Transmit Loop Timer 2. In
the preferred embodiment, Signal 2 is a 2100 Hz tone and Transmit Loop
Timer is set for 2650 ms. Thereafter, the process continues at block 82,
which illustrates execution of subroutine 1. Subroutine 1 is described
above with reference to FIG. 2c.
Thus, in the preferred embodiment, the 2100 Hz tone is a required part of
the CCITT V.25 auto-answer protocol. Scanning for a 390 Hz response tone
for 140 ms allows for the detection of certain V.23 configured modems.
And, by scanning for a 980 Hz response tone, certain V.21 configured
modems are detected.
Referring still to FIG. 2a, block 84 illustrates a determination of whether
or not a response tone was received during execution of subroutine 1,
shown in FIG. 2c. If a response was received, data communications are
established as shown in block 78. If a response was not received, the
process continues at block 86 which depicts the initiation of a
transmission of Signal 3 and setting a selected Transmit Loop Timer 3. In
the preferred embodiment, Signal 3 is silence and Transmit Loop Timer is
set for 75 ms.
The process then passes to block 88, which depicts execution of subroutine
2. Subroutine 2 is illustrated in FIG. 2d. Subroutine 2 begins at block
90, and thereafter passes to block 92 which depicts setting a receiver to
scan for a 980 Hz tone and setting the receiver timer for 60 ms. Block 94
illustrates a determination of whether or not a response tone of 980 Hz is
received. If a response tone is received, a particular data communication
device type and transmission speed are determined and data communications
are established, as shown in block 96.
If a determination is made that a response tone of 980 Hz is not received,
the process passes to block 98 where a determination is made as to whether
or not the Transmit Loop Timer is timed out. If the Transmit Loop Timer is
timed out, the process jumps to block 106, which illustrates subroutine 2
returning to the main program.
Referring again to block 98, if a determination is made that the Transmit
Loop Timer is not timed out, the process passes to block 100 which depicts
a determination of whether or not the receiver timer is timed out. If the
receiver timer is not timed out, the process passes to block 102 which
illustrates a determination of whether or not the global timer is timed
out.
If the global timer is timed out, data communications have not been
established and block 104 shows an error code is posted and the
transmission line is disconnected. If the global timer is not timed out,
the process returns to block 94 to continue scanning for a 980 Hz response
tone. Finally, referring again to block 100, if a determination is made
that the receiver timer is timed out, subroutine 2 returns to the main
program, as illustrated in block 106.
Thus, in the preferred embodiment, subroutine 2 is utilized to detect FSK
configured modems. The 75 ms of silence is a required part of the CCITT
V.25 auto-answer protocol. By transmitting silence for 75 ms and scanning
for a 980 Hz response tone for 60 ms, certain V.21 configured modems are
detected.
Referring again to FIG. 2a, block 108 illustrates a determination of
whether or not a response tone was received during execution of subroutine
2, shown in FIG. 2d. If a response was received, data communications are
established as shown in block 78. If a response was not received, the
process continues at block 110 with the initiation of a transmission of
Signal 4 and setting a selected Transmit Loop Timer 4. In the preferred
embodiment, Signal 4 is a 1300 Hz tone and Transmit Loop Timer is set for
350 ms.
The process then continues at block 112, which depicts execution of
subroutine 3. Subroutine 3 is illustrated in FIG. 2d. Subroutine 3 begins
at block 114, and thereafter passes to block 116 which depicts setting a
receiver to scan for a 390 Hz tone and setting the receiver timer for 350
ms. Block 118 illustrates a determination of whether or not a response
tone of 390 Hz is received in response to transmitting Signal 4. If a
response tone is received, a particular data communication device type and
transmission speed are determined and data communications are established,
as shown in block 120.
If a determination is made that a response tone of 390 Hz is not received,
the process passes to block 122 where a determination is made as to
whether or not the Transmit Loop Timer is timed out. If the Transmit Loop
Timer is timed out, the process jumps to block 130, which illustrates
subroutine 3 returning to the main program.
Referring again to block 122, if a determination is made that the Transmit
Loop Timer is not timed out, the process passes to block 124 which depicts
a determination of whether or not the receiver timer is timed out. If the
receiver timer is not timed out, the process passes to block 126 which
illustrates a determination of whether or not the global timer is timed
out.
If the global timer is timed out, data communications have not been
established and block 128 depicts the posting of an error code and
disconnecting the transmission line. If the global timer is not timed out,
the process returns to block 118 to continue scanning for a 390 Hz
response tone. Referring again to block 124, if a determination is made
that the receiver timer is timed out, subroutine 3 returns to the main
program, as illustrated in block 130.
Thus, in the preferred embodiment, subroutine 3 is utilized to detect FSK
configured modems. By transmitting a 1300 Hz tone for 350 ms and scanning
for a 390 Hz response tone for 350 ms, certain V.23 configured modems are
detected.
Referring again to FIG. 2a, block 132 illustrates a determination of
whether or not a response tone was received during execution of subroutine
3, shown in FIG. 2c. If a response was received, data communications are
established as shown in block 78. If a response was not received, the
process continues at block 134 with the initiation of a transmission of
Signal 5 and setting a selected Transmit Loop Timer 5. In the preferred
embodiment, Signal 5 is silence and Transmit Loop Timer is set for 300 ms.
Thereafter, the process passes to block 136, which depicts execution of
subroutine 1. In the preferred embodiment, subroutine 1 is utilized to
detect FSK configured modems. Transmitting silence for 300 ms is performed
to streamline detection of PSK modems during execution of subroutine 4,
which is described in greater detail below. Scanning for a 390 Hz response
tone for 140 ms detects certain V.23 configured modems, and scanning for a
980 Hz response tone detects certain V.21 configured modems.
Referring still to FIG. 2a, block 138 illustrates a determination of
whether or not a response tone was received during execution of subroutine
1, shown in FIG. 2c. If a response was received, data communications are
established as shown in block 78. If a response was not received, the
process continues at block 140 with the initiation of a transmission of
Signal 6 and setting a selected Transmit Loop Timer 6. In the preferred
embodiment, Signal 6 comprises unscrambled 1 bits and Transmit Loop Timer
is set for 1600 ms.
Thereafter, the process continues at block 142, which depicts execution of
subroutine 4. Subroutine 4 is illustrated in FIG. 2f. Subroutine 4 is
utilized in the preferred embodiment to detect PSK configured modems, and
begins at block 144. Block 146 illustrates setting a receiver to scan for
initial PSK signals and setting the target number of scrambled 1 bits to
be detected. The present invention detects PSK modems not by tones or
frequencies, as known in the prior art, but by looking for specific
strings of binary 1's and 0's. The process then passes to block 148 which
depicts clearing certain PSK flag bits and ensures the bit counter has
been set for the target number of scrambled 1 bits.
Block 150 illustrates a determination of whether or not a response signal
is received. If a response signal is received, the modem is known to be a
V.22 bis modem, and data communications are established, as shown in block
152. If a response signal is not received, the process passes to block 154
which depicts a determination of whether or not the number of scrambled 1
bits received is greater or equal to the target number.
If the number of scrambled 1 bits is greater or equal to the target number,
the calling modem is assumed to be a V.22 modem and data communications
are established as shown in block 152. Referring again to block 154, if a
determination is made that the number of scrambled 1 bits is not greater
or equal to the target number, the process passes to block 156 which
illustrates a determination of whether or not the Transmit Loop Timer is
timed out. If the Transmit Loop Timer is not timed out, the process
continues at block 158 with a determination of whether or not the global
timer is timed out.
If the global timer is timed out, data communications have not been
established and block 160 illustrates an error code is posted and the
transmission line is disconnected. If the global timer is not timed out,
the process returns to block 150 to continue to scanning for a response
signal. Lastly, referring again to block 156, if a determination is made
that the Transmit Loop Timer is timed out, subroutine 4 returns to the
main program, as shown in block 162.
Referring again to FIG. 2a, block 164 illustrates a determination of
whether or not a response signal was received during execution of
subroutine 4, shown in FIG. 2f. If a response was received, data
communications are established as shown in block 78. If a response was not
received, the process continues at block 166 with the initiation of a
transmission of Signal 7 and setting a selected Transmit Loop Timer 7. In
the preferred embodiment, Signal 7 is a 1300 Hz tone and Transmit Loop
Timer is set for 1600 ms.
The process then continues at block 168, with FIG. 2b which depicts
execution of subroutine 1. Subroutine 1 is described above with reference
to FIG. 2c. In the preferred embodiment, subroutine 1 is utilized to
detect FSK configured modems. A 1300 Hz tone is the starting signal for
V.23 modems and is disregarded by V.21 modems. Thus, scanning for a 390 Hz
response tone for 140 ms detects certain V.23 configured modems. And, by
scanning for a 980 Hz response tone, certain V.21 configured modems are
detected.
Referring still to FIG. 2b, block 170 illustrates a determination of
whether or not a response signal was received during execution of
subroutine 1. If a response was received, data communications are
established as shown in block 78. If a response was not received, the
process continues at block 172 with the initiation of a transmission of
Signal 8 and setting a selected Transmit Loop Timer 8. In the preferred
embodiment, Signal 8 is silence and Transmit Loop Timer is set to 20 ms.
After Transmit Loop Timer 8 is timed out, the process passes to block 174,
which depicts the initiation of a transmission of Signal 9 and setting a
selected Transmit Loop Timer 9. In the preferred embodiment, Signal 9 is a
1300 Hz tone and Transmit Loop Time is set for 130 ms.
Thereafter, the process continues at block 176, which illustrates execution
of subroutine 1. Subroutine 1 is described above with reference to FIG.
1c, and is utilized to detect either V.21 or V.23 modems.
Continuing to refer to FIG. 2b, block 178 depicts a determination of
whether or not a response tone was received during execution of subroutine
1. If a response was received, data communications are established as
shown in block 78. If a response was not received, the process continues
at block 180 which illustrates initiating a transmission of Signal 10 and
setting a selected Transmit Loop Timer 10. In the preferred embodiment,
Signal 10 is a 1650 Hz tone and Transmit Loop Time is set for 4900 ms.
Thereafter, the process passes to block 182, which illustrates execution of
subroutine 1. A 1650 Hz tone is the starting signal for V.21 modems and
is disregarded by V.23 modems. Subroutine 1 is described above with
reference to FIG. 2c, and is utilized to detect either V.21 or V.23
modems.
Referring still to FIG. 2b, block 184 depicts a determination of whether or
not a response tone was received during execution of subroutine 1. If a
response was received, data communications are established as shown in
block 78. If a response was not received, the process continues at block
186 which illustrates initiating a transmission of Signal 11 and setting a
selected Transmit Loop Timer 11. In the preferred embodiment, Signal 11 is
silence and Transmit Loop Time is set for 300 ms.
Thereafter, the process continues at block 188, which depicts execution of
subroutine 1. Subroutine 1 is described above with reference to FIG. 2c,
and is utilized to detect either V.21 or V.23 modems.
Continuing to refer to FIG. 2b, block 190 illustrates a determination of
whether or not a response tone was received during execution of subroutine
1. If a response was received, data communications are established as
shown in block 78. If a response was not received, the process passes to
block 192 which depicts initiating a transmission of Signal 12 and setting
a selected Transmit Loop Timer 12. In the preferred embodiment, Signal 12
is unscrambled one bits and Transmit Loop Timer is set for 1600 ms.
Thereafter, the process continues at block 194, which depicts execution of
subroutine 4. Subroutine 4 is described above with reference to FIG. 2f,
and is utilized to detect V.22 bis or V.22 modems.
Referring still to FIG. 2b, block 196 illustrates a determination of
whether or not a response was received during execution of subroutine 4.
If a response was received, data communications are established as shown
in block 78. If a response was not received, the process passes to block
198 which depicts initiating a transmission of Signal 13 and setting a
selected Transmit Loop Timer 13. In the preferred embodiment, Signal 13 is
a 1300 Hz tone and Transmit Loop Time is set for 4900 ms.
Thereafter, the process passes to block 200, which illustrates execution of
subroutine 1. Subroutine 1 is described above with reference to FIG. 2c,
and is utilized to detect either V.21 or V.23 modems.
Continuing to refer to FIG. 2b, block 202 depicts a determination of
whether or not a resp | | |
