JPS63114359A - Method for switching communication mode - Google Patents

Abstract

PURPOSE:To easily return to voice mode even if changeover to MODEM mode takes place in error in the voice mode by using the detection of a voice signal in switching the MODEM mode into the voice mode. CONSTITUTION:In switching the system from the MODEM mode into the voice mode, the voice signal is used. In order to realize it, a voice signal detection circuit 7 and a training signal detection circuit 8 are provided respectively to the transmission line for the MODEM mode and the voice mode signal of a changeover device 4 and the changeover switch 6 is switched by the output of both the detection circuits. Even if the MODEM mode is selected in error when the communication system is in the voice mode, since the silence of a talker for a long time hardly takes place in general, the voice mode is restored easily through the detection of a voice signal.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a communication mode switching method, particularly a communication mode of a communication system that switches between a voice communication device such as a telephone and a modem communication device such as a fax machine. Regarding the switching method.

(Prior Art) A communication system that transmits and receives signals by appropriately switching between voice communication such as a telephone and communication via a modem such as a fax is based on a telephone 1 as shown in FIG.
and a modem 2 are connected in parallel, and when the fax 3 or the telephone 1 is used, the switching device 4 detects a predetermined signal with its built-in detection circuit 5 and switches the changeover switch 6. The mode is switched to fax (modem) mode or voice mode, respectively.

As a method for performing the above-mentioned switching, conventionally, the method shown in FIG.
) When the system is in voice mode, it detects the training signal that appears at the beginning of the modem signal and switches to modem mode, and when the system is in modem mode, it detects the absence of the signal. The common method was to switch to voice mode.

However, with the mode switching method described above, even if the system mistakenly recognizes a voice signal as a training signal when it is in voice mode and switches to modem mode, the speaker will not be silent for a long time during voice transmission. The flaw is that it is extremely difficult to return to voice mode because it is generally inconceivable.

(Object of the Invention) The present invention has been made to eliminate the deficiencies of the conventional communication mode switching method as described above. It is an object of the present invention to provide a communication mode switching method that allows easy return to voice mode.

(Summary of the Invention) In order to achieve the above-mentioned object, a communication mode switching method according to the present invention switches from modem mode to voice mode by detecting a voice signal.

(Examples) The present invention will be explained in detail below using examples shown in the drawings.

FIG. 1(a) is a state transition diagram illustrating a communication mode switching method according to the present invention when switching the system from modem mode to voice mode.

Indicates that it is based on an audio signal. In order to realize this, for example, the method shown in FIG. 3(b) may be used.

That is, the detection port built into the cutting wedge device 4 in FIG. 2(a)! 35, an audio signal detection circuit 7 and a training signal detection circuit 8 may be provided in the modem mode and audio mode signal transmission laben, respectively, and the changeover switch 6 may be switched by the output of these rain detection circuits. , as the audio signal detection circuit l@3(a)K
As shown, basically the spectrum of the audio signal is
Energy concentrates below IKHz, and the spectrum of the modem signal changes as shown in the same figure (bl), where the above relationship is reversed.
．． A circuit may be used that compares the energy around 5 KHz and determines that it is an audio signal if the difference between the two is a certain value or more.

Further, the spectrum of the training signal is, for example, 9
In the case of 600 bps (CCITT Recommendation V29), it is noted that it is a composite sine wave with three frequencies within the audio band as shown in the same figure (c), and it is detected that only the above three frequency components have arrived. do it.

In order to detect the above-mentioned audio signal, for example, the method shown in FIG. 4 (al.
The comparator 12 compares the outputs of the bandpass filters 9 and 10 of K<0.5KH2 and 2.5KH2 via the integrator 11, and if the difference in energy between the two is greater than a predetermined value, the audio signal is is determined to have arrived. In addition, in order to detect the training signal, for example, as shown in FIG. A comparator 16 compares the output obtained by adding the energies of the three frequency components obtained by the adder 16 with the total signal energy obtained from the input signal via the integrator 11. At this time, if the addition output is greater than or equal to a predetermined value and the difference between the addition output and the total signal energy is less than or equal to the predetermined value, it is determined that the training signal has arrived. At this time, a bandpass filter that constitutes the detection circuit,
The integrator, adder, and comparator may be constructed from either analog circuits or digital circuits.

By using such a sensor, even if the system erroneously recognizes an audio signal as a training signal and switches to modem mode when in audio mode &C6, it can easily return to audio mode.

The audio signal detection circuit shown in Figure J (al) above is a basic one, and when applied to an actual product, the sampling frequency should be increased, that is, the number of bandpass filters should be increased to perform accurate spectrum analysis. It goes without saying that this should be done. (Effect of the Invention) Since the present invention is constructed as described above, even if the communication system is in the voice mode and accidentally switches to the modem mode, the speaker Since it is generally not possible to remain silent for a long period of time, detection of an audio signal has a significant effect in easily returning to the audio mode.

Although the configuration of the device becomes somewhat complicated to provide such a function, the improved performance of the 9 communication system more than compensates for this.

[Brief explanation of the drawing]

Figure 1 (at is a diagram explaining the concept of the communication mode switching method according to the present invention, Figure 2 (b) is a block diagram showing one embodiment for realizing this, and Figure 2 (a) is a diagram explaining the concept of the communication mode switching method according to the present invention. A block diagram of the communication mode switching device, FIG. and (bl are block diagrams showing one embodiment of the audio signal and training signal detection circuits used in the present invention, respectively. 1... Voice communication device, 2.
・・・・・・・・・Modem, 3・・・・・・・・・
Communication device via modem, 4...
switching device. 5.8 and 7... Signal detection device.

Claims (1)

[Claims] In a communication system that switches between a communication device using voice and a communication device via a modem, the arrival of a voice signal when the communication system is in the modem mode, and the arrival of a training signal for the modem when the communication system is in the voice mode. A communication mode switching method characterized in that the communication mode is determined by detecting the communication mode.