JPH02296452A - Still picture video telephone system - Google Patents

Abstract

PURPOSE:To attain efficient communication without sending at undesired picture by requesting the stop of picture transmission from a reception side to a transmission side during picture transmission and restarting voice communication automatically. CONSTITUTION:When the stop of communication of a picture signal is desired at the reception-side, a changeover switch 20 is switched to the position of a tone generator 18. When a signal from a telephone circuit is superimposed with the tone of a prescribed frequency, a tone detector 19 detects the tone at the transmission side to inform it to a CPU 11. The CPU 11 receiving the notice is acted as a call restarting means to stop the transmission of the picture signal and switches a matrix switch 5 so that the analog circuit 4 and a telephone interface circuit 6 are connected and the voice talking is restored.

Description

Detailed Description of the Invention [Industrial Application Field] This invention modulates the phase and amplitude of a still image signal captured by a camera into an audio band signal and sends it out to a telephone line, and also transmits the signal to a telephone line. The present invention relates to a still image videophone device that demodulates a signal and displays an image on a display device.

[Conventional technology]

There is a demand for videophones that can simultaneously send voice and images using telephone lines, but in reality, with current telephone lines, it is difficult to continuously send and receive dynamic images, which require a huge amount of data. Still image videophone devices that transmit still images to the other party during a call are being put into practical use.

This still image videophone device temporarily interrupts a normal voice call and sends a desired still image, such as the speaker's face, a photo screen, or a picture depending on the content of the call. Is possible.

Therefore, according to such a still image videophone device, it is possible to send and receive images over a telephone line, which was previously impossible, and the amount of data processing is also limited because only one still image is sent each time. This has the advantage that it is easy to put the videophone device into practical use.

A video telephone device capable of transmitting still images as described above is disclosed, for example, in the October 1986 issue of Foreign Communication Technology. FIG. 4 is a circuit configuration diagram of a monochrome simple still picture video telephone.

In the figure, (1) is a handset, (2) is a microphone, (3) is an audio input/output circuit, (4) is an analog circuit, (
5) is a matrix switch, (6) is a telephone interface (1/F) circuit, (7) is a telephone line connection terminal, and (8) is a telephone interface (1/F) circuit.
) is the speaker, (9) is the key bat, (10) is the input/output board, (11) is the CPU, (12) is the program memory, (13a) is the modulation circuit, (13b) is the demodulation circuit, (
14) is a television camera, (15) is an image controller, (16) is an image memory, and (17) is a display. Further, FIG. 5 is a sequence diagram showing an image transmission procedure of the video telephone device.

Next, the operation of audio and image signal transmission in the conventional video telephone will be explained based on FIGS. 4 and 5.

For voice calls, use the handset (1) or microphone (
2) to audio input/output circuit (3), analog circuit (4),
The signal is sent to the telephone line connection terminal (7) via the matrix switch (5) and the telephone interface circuit (6). Further, an audio signal from the other party is reproduced by the handset (1) or the speaker (8) via a path opposite to the above-mentioned signal path.

On the other hand, when transmitting an image signal, first, an ID code is sent to confirm whether the other party is a videophone device of the same data type, and after confirming that the other party has returned the ID code, Sends image data.

In other words, in Fig. 4, when an instruction is given to send an image using the keypad (9), the
The PU (11) detects this and stores the program memory (1
2) The ID code is sent to the modulation circuit (13a) according to the program stored in advance. After modulating this ID code into an analog signal, it is sent out from the telephone line connection terminal (7) via the matrix switch (5).

The ID code from the communication partner passes through a path opposite to the above signal path, and the CPU (11) confirms the ID code. During this time, the images captured by the television camera (14) are quantized by the image controller (15), stored in the image memory (16), and sequentially derived and displayed on the display (17).
The image is output from the image memory (16) to the telephone line connection terminal (7) in response to a command from the CPU (11).

When an ID code or image data is input from the other party, the carrier signal received by the matrix switch (5) converts the received signal from the telephone interface circuit (6) from the analog circuit (4) to the demodulation circuit (13).
Switch to b).

After the received signal is demodulated by the demodulation circuit (13b), the CPU (11) returns the ID code and stores the data in the image memory (16), and the image controller (15) transfers the image data and the other party's image. The data is sequentially derived and displayed on the display (17).

Note that after the transmission and reception of the image is completed, the modulation/demodulation circuit (13a),
When the carrier signal from (13b) disappears, the matrix switch (5) switches to the telephone interface circuit (6).
) and the analog circuit (4) to restore voice communication.

[Problem to be solved by the invention]

Since the conventional still image video telephone device is configured as described above, the transmission of an image cannot be stopped midway through the transmission of an image. In particular, image transmission can also be stopped if it is determined that the image being received is an unnecessary image, or if sufficient image information has been obtained midway through and it is determined that further transmission is unnecessary. There were some problems, such as the inability to restore voice calls.

The present invention has been made to solve the above-mentioned problems, and aims to provide a still image video telephone device that can stop image transmission during reception and restore voice communication. purpose.

[Failure to solve the problem]

The still image video telephone device according to the present invention includes a tone generator that outputs a tone indicating a request to terminate image transmission when receiving, a tone detector that detects the tone when transmitting, and a tone detector that detects the tone when transmitting. The present invention is equipped with a call resuming means for resuming a call using an interrupted voice.

[Effect]

In this invention, during image transmission, the receiver sends a tone requesting termination of image transmission, and when the transmitting side detects this tone, image transmission is terminated and voice communication is resumed. This eliminates the need to transmit images, making it possible to perform efficient communication.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, in which the same parts as in FIG. 4 are given the same reference numerals and redundant explanations are omitted, (18) is a tone generator that generates a tone for requesting termination of image transmission, and (19) is a tone generator that detects this tone. Tone detection W (20) is a changeover switch that selectively connects the matrix switch (5) and tone generation 1W (1B) to the telephone interface circuit (6).

FIG. 2 shows an example of tone frequencies. (
Analog telephone band still image video communication system (JJ4) standardized by the Telegraph and Telephone Technical Committee (TTC)
0,10) J, the carrier frequency on the transmitting side is defined as 1748 Hz and the modulation rate as 1748 baud.

Therefore, assuming that the filter in the modulation/demodulation circuit is ideal, the frequency bandwidth occupied by the transmission signal is 1748±1748/2 Hz. Since the frequency bandwidth of general telephone lines is 300 to 3400Hz, the second
As shown in the figure, the band 300-874Hz or 2
The tones may be placed within 622-3400 Hz.

Next, the operation of the above embodiment will be explained with reference to the sequence diagram shown in FIG. The switch (20) normally connects the matrix switch (5) and the telephone interface circuit (6) and is in a receiving state.

Now, in the above reception state, if you want to cancel image signal communication on the receiving side, switch the changeover switch (20) to the tone generator (18) side and cancel image signal communication. The tone output from the tone generator (18) is sent out from the telephone line connection terminal (7) via the telephone interface circuit (6).

On the other hand, on the transmitting side, if a tone of a predetermined frequency is superimposed on the signal from the telephone line, a tone detector (19) detects this tone and notifies the CPU (11). Upon receiving this notification, the CPU (11) operates as a call resuming means, stops sending out the image signal, and switches the matrix switch (5) to connect the analog circuit (4) and telephone interface circuit (6). This will restore voice calls.

Note that the tone detection circuit may include, for example, a bandpass filter for tones, and detect tones based on the output thereof.

Further, in the above embodiment, the case where the tone has a frequency lower than that of the image signal region is shown in FIG. 2, but it may have a frequency higher than that of the image signal region.

Further, although FIG. 2 shows the case where there is a single tone, there may be several tones. This is because it is rare for noise to exist in all of the plurality of frequencies employed, and the influence of malfunctions due to noise is smaller in this case.

Furthermore, in the above embodiment, the modulated signal is output directly to the telephone line, but in order to prevent malfunction of the tone detector, a bandpass filter is inserted after the modulation circuit to limit the band of the modulated signal. It's okay.

〔Effect of the invention〕

As described above, according to the present invention, the receiving side requests the transmitting side to terminate the image transmission during image transmission and is configured to automatically restart the voice call, so that unnecessary images can be sent. This has the effect of making it possible to make efficient calls without any hassle.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a still image video telephone device according to an embodiment of the present invention, FIG. 2 is a frequency band diagram showing tone frequency bands, and FIG. FIG. 4 is a block diagram showing the configuration of a conventional still image video telephone device, and FIG. 5 is an explanatory diagram of a communication procedure by the conventional device. In the figure, (11) is a CPU, (18) is a tone generator, (19) is a tone detector, and (20) is a changeover switch. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Patent Attorney Masuo Oiwa (2 others) Chart procedural amendment (voluntary)

Claims (1)

[Claims] A still image signal captured by a camera is phase-amplitude modulated into an audio band signal and sent to a telephone line, and the image signal supplied from the telephone line is demodulated and displayed as an image on a display device. A still image video telephone device includes: a tone generator that indicates a request to terminate image transmission outside the modulated signal band; and a changeover switch that switches and connects the modulator that outputs the modulated signal and the tone generator to the telephone line. , a tone detector that detects the tone from a signal input from the telephone line, and a call resuming means that suspends image transmission and resumes voice communication by receiving the tone detection signal from the tone detector. A still image videophone device characterized by comprising: