Pulse or digital communications – Transceivers – Modems
Reexamination Certificate
1997-09-15
2001-09-18
Chin, Stephen (Department: 2634)
Pulse or digital communications
Transceivers
Modems
C370S296000, C379S100170, C358S434000, C358S435000
Reexamination Certificate
active
06292509
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to data-communication apparatuses and methods, and in particular, to a data-communication apparatus and method for performing data communication by using a modem with a plurality of modulation/demodulation modes which is controlled by the data-communication apparatus to modulate/demodulate signals in a mode specified from among the modulation/demodulation modes.
2. Description of the Related Art
Conventional data-communication apparatuses of this type include, for example, a facsimile apparatus. Concerning the facsimile apparatus, increasing its transmission speed is in progress. The International Telecommunications Union (ITU) has recommended a communication protocol (V.34) using a V.34-modem with a maximum transmission speed of 33.6 kilobits/second (kbps) which exceeds the 14.4 kbps obtained by a conventional V.17-modem, and the V.8 protocol for specifying a modem to be used when line connection to another unit is established. The V.34 protocol and the V.8 protocol will be hereinafter treated as new protocols. Although increasing the transmission speed is effective in reducing communication costs, it is required that a facsimile apparatus as a communication apparatus have a protocol capable of achieving a faster transmission speed, and maintain compatibility with conventional facsimile apparatuses.
When performing automatic reception, a conventional facsimile apparatus having both the new and conventional protocols sends a signal ANSam (representing the V.8 protocol and being a 2100-Hz modified tone) compatible with the conventional protocol signal CED. When the other apparatus receives the signal ANSam, it sends a new protocol signal CM (which is a call-activation menu signal, which is used to represent a usable modulation method, and which is a 300-bps signal modified in the V.21 low-range channel). When the facsimile apparatus receives the signal CM within a reference time, it sends a signal JM (which is a common menu signal and is a 300-bps signal modulated in the V.21 high-range channel) representing a usable modulation method for both apparatuses, based on the signal CM and its own function. On receiving the signal JM, the other apparatus sends a signal CJ (which represents a termination of the signal CM and is a 300-bps signal modulated in the V.21 low-range channel). In this manner the facsimile apparatus communicates with a modem using the modulation method represented by the signal JM. Half-duplex communication with the V.34-modem, designated by the signal JM, shifts the protocol for the facsimile apparatus to the V.34 protocol. In addition, when the facsimile apparatus sends the signal ANSam, and cannot receive the signal CM within the predetermined time, it determines that the other apparatus is a conventional one, and transmits a conventional signal DIS in the T.30 protocol which is modulated in the V.21 high-range channel. The facsimile apparatus receives a signal DCS modulated in the V.21 high-range channel.
When the other apparatus performs manual transmission, and starts a transmission operation after the signal ANSam ends, it does not send the signal CM and the signal CJ. Accordingly, the facsimile apparatus sends the conventional T.30 protocol signal DIS. In this case the signal DIS is sent, with the signal DIS being provided with information representing possession of the V.8 protocol-functions so that the T.30 protocol can shift to the new protocol. The signal DIS causes the other apparatus to recognize that the receiver apparatus has the V.8 protocol. If the other apparatus has recognized that the receiver apparatus has new protocol functions, it sends a signal CI (being a call-activation display signal and a 300-bps signal modulated in the V.21 low-range channel) representing a return to the V.8 protocol. If the other apparatus has recognized the receiver apparatus has no new-protocol functions, it sends a signal DCS (300-bps signal modulated in the V.21 high-range channel) in the T.30 protocol.
In order to cope with the above circumstances, the receiver apparatus must have a structure capable of simultaneously detecting the signal CI modulated in the V.21 low-range channel (L) and the signal DCS modulated in the V.21 high-range channel (H).
Conventionally, the two channels: the V.21 low-range channel (L) and the V.21 high-range channel (H) are used for full-duplex communication. Conventional facsimile apparatuses use the V.21 modem for only half-duplex communication, and have no structure capable of simultaneously receiving signals in the two channels. In other words, setting the V.21-modem in the high-channel mode (H-channel mode) for receiving the signal DCS hinders the V.21-modem from receiving the signal CI in the low-range channel. Also, setting the V.21-modem in the low-range channel mode (L-channel mode) for receiving the signal CI hinders the V.21-modem from receiving the signal DCS in the high-range channel.
To overcome this problem, by using a plurality of V.21-modems, it is possible that one end receives a signal in the low-range channel and another end receives a signal in the high-range channel. However, such a structure is complicated.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to improve a conventional data-communication apparatus in view of the foregoing problems.
Another object of the present invention is to distinguish signals in a plurality of modulation modes which may be simultaneously received, without using a complicated structure.
A further object of the present invention is that, even if a modem incapable of simultaneously distinguishing signals in a plurality of modulation modes is used, signals in a plurality of modulation modes which may be simultaneously received can be received.
To this end, according to an aspect of the present invention, the foregoing objects have been achieved through provision of a data-communication apparatus for performing data communication by using a modem with a plurality of modulation/demodulation modes, operated in a mode specified from among the plurality of modulation/demodulation modes, the data-communication apparatus comprising: frequency-detection means for detecting the frequency of a received signal; and control means for specifying the operation mode of the modem, and changing the operation mode of the modem in accordance with the detection obtained by the frequency-detection means, wherein the frequency of a signal in the modulation/demodulation mode being not specified by the control means is detected by the frequency-detection means while the modem is operating in the specified mode, and the detection of the frequency causes a change of the operation mode of the modem so that the plurality of modulation/demodulation modes are capable of being distinguished.
According to another aspect of the present invention, the foregoing objects have been achieved through provision of a data-communication method using a modem with a plurality of modulation/demodulation modes, operated in a mode specified from among the plurality of modulation/demodulation modes, the data-communication method comprising the steps of: detecting the frequency of a received signal; specifying the operation mode of the modem, and changing the operation mode in accordance with the frequency detection; and detecting the frequency of a signal in the modulation/demodulation mode being not specified by the control means while the modem is operating in the specified operation mode, and changing the operation mode of the modem by the frequency detection so that the plurality of modulation/demodulation modes are capable of being distinguished.
REFERENCES:
patent: 4215243 (1980-07-01), Maxwell
patent: 4908851 (1990-03-01), Kotani et al.
patent: 5025469 (1991-06-01), Bingham
patent: 5153897 (1992-10-01), Sumiyoshi et al.
patent: 5153912 (1992-10-01), Sakakibara et al.
patent: 5185783 (1993-02-01), Takahashi et al.
patent: 5293575 (1994-03-01), Hirai
patent: 5450472 (1995-09-01), Brax
patent: 5721731 (1998-02-0
Canon Kabushiki Kaisha
Chin Stephen
Fitzpatrick ,Cella, Harper & Scinto
Liu Shuwang
LandOfFree
Data-communication apparatus and method for modulation or... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Data-communication apparatus and method for modulation or..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data-communication apparatus and method for modulation or... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2488243