JPH01288081A - Television telephone system - Google Patents

Abstract

PURPOSE:To attain transmission reception of a picture data without intermitting voice conversation by providing a low pass filter(LPF) applying band control of audio data, a high pass filter(HPF) applying the band control of picture data, an adder circuit synthesizing the audio data and the picture data and a single side band amplitude demodulation section. CONSTITUTION:When the picture data is not sent, the audio data outputted from a telephone section 2 is inputted directly to an LPF 8 not through an LPF 6. In this case, a changeover control section 4 is controlled so as to close the contacts of a changeover switch 5. On the other hand, the audio data and the picture data subjected to frequency multiplex are separated by the LPF 9 and the HPF 10 in the reception. The LPF 9 passes the audio data only and the HPF 10 passes only the picture data. The audio data passing through the LPF 9 is sent to the telephone section 2, the picture data passing through the HPF 10 is demodulated into the normal picture data by a single side band amplitude demodulation section 11 an fed to the picture processing section 3. Thus, the voice conversation is attained even during the period when the picture data is sent.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a video telephone device that transmits and receives audio data and image data over a general analog telephone line.

(Prior Art) In recent years, inexpensive videophone devices that use general analog telephone lines have appeared. FIG. 2 is a block diagram of a conventional video telephone device. In FIG. 2, 1 is a general analog telephone line, 2 is a telephone unit that sends and receives audio, 3 is an image processing unit that sends and receives image data, 4 is a switching control unit,
5 is a changeover switch.

Next, the operation of the conventional example will be explained. In Figure 2,
Other than when transmitting image data, that is, when transmitting and receiving audio data and when receiving image data, the changeover control section 4 closes the b contact side of the changeover switch 5, so that the telephone section 2 is in the normal state. Connected to analog telephone line 1. Furthermore, when transmitting image data, the a-contact side of the changeover switch 5 is set to be closed under the control of the changeover control section 4, thereby making it possible to transmit and receive audio data and image data.

(Problems to be Solved by the Invention) However, in the videophone device with the above conventional configuration,
There was a problem in that it was not possible to have a voice conversation while sending the image data.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a video telephone device that allows voice conversation even while image data is being transmitted.

(Means for Solving Problem 111) In order to achieve the above object, the present invention provides a low-pass filter that limits the band of audio data, a high-pass filter that limits the band of one image data, and a combination of the audio data and the image data. It includes an adder circuit for synthesizing data, a low-pass filter for band-limiting the output from the adder circuit, and a single sideband amplitude demodulator.

(Function) With the above-described configuration, the present invention has an effect of making it possible to transmit or receive audio data and image data simultaneously by frequency multiplexing and dividing the audio data and image data.

(Embodiment) FIG. 1 shows the configuration of a video telephone device according to an embodiment of the present invention. In FIG. 1, 1 is an analog telephone line, and 2 is a telephone unit that transmits and receives voice.

3 is an image processing unit that transmits and receives image data, 4 is a switching control unit, 5 is a changeover switch, and 6 is a low-pass filter (hereinafter referred to as LP) that limits the band of audio data when transmitting image data.
7 is an addition circuit that adds the transmitted rain image data and the band-limited audio data, and 8 is an LPF that limits the band of the transmitted data.

9 is an LP that passes only the low frequency components of the received data.
F, 10 is a high-pass filter (hereinafter referred to as HPF) that passes only the high-frequency components of the received data, 11 is a single sideband amplitude demodulator, and 12 is an HPF that removes the lower sideband.

Next, the operation of the above embodiment will be explained. When transmitting one image data in the above embodiment.

A high frequency component is removed from the audio data outputted from the telephone section 2 by an LPF 6, a lower sideband of the image data of the high frequency component outputted from the first image processing section 3 is removed by an HPF 12, and the summation circuit 7 adds the high frequency components. At this time, the changeover control unit 4 controls the changeover switch 5 to
Controls the side contacts to close. The LPF 8 limits the bandwidth of the added data, and a frequency-multiplexed signal of audio data and image data is output to the general analog telephone line 1.

Furthermore, when image data is not being transmitted, the audio data output from the telephone section 2 is input directly to the LPF 8 without passing through the LPF 6. At this time, the switching control section 4 is controlled so that the b-side contact of the changeover switch 5 is closed. On the other hand, for reception, frequency-multiplexed audio data and image data are
Separate with F9 and HPFIO. The LPF9 passes only audio data, and the HPFIO passes only image data. The voice data that has passed through the LPF 9 is sent to the telephone section 2.

In addition, the image data that has passed through the HPFIO is demodulated into regular image data by the single sideband amplitude demodulation section 11 and is then demodulated into regular image data by the image processing section 3.
sent to.

As described above, according to the above embodiment, the LPF limits the band of audio data, and the HPF limits the band of image data.
By providing an adder circuit that synthesizes the audio data and image data, an LPF that limits the band of the output from the adder circuit, and a single sideband amplitude demodulator, voice conversation can be maintained even while image data is being transmitted. can do.

(Effects of the Invention) As is clear from the above embodiments, the present invention includes an LPF that limits the band of audio data, an HPF that limits the band of image data, an adder circuit that synthesizes the audio data and image data, and a single side filter. By providing the waveband amplitude demodulation section, there is an effect that image data can be transmitted and received without interruption of voice conversation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a video telephone device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional video telephone device. 1...Analog telephone line, 2...Telephone section, 3...
- Image processing section, 4... switching control section. 5... Selector switch, 6, 8, 9... LPF,
10, 12...HPF, 11...Single sideband amplitude demodulation section. Patent applicant Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] A low-pass filter that is connected to an analog telephone line and limits the band of audio data, a high-pass filter that limits the lower side band of image data, an adder circuit that synthesizes the audio data and image data, and A videophone device comprising a low-pass filter that band-limits the output from the circuit and a single sideband amplitude demodulator.