JPS62193472A - Information transmission system - Google Patents

Abstract

PURPOSE:To transmit bits of picture and sound information simultaneously with one telephone line, by dividing a frequency band area of 2400Hz, and transmitting a sound signal on a low-pass area, and a picture signal on a high- pass area. CONSTITUTION:A television signal image-picked up with a television camera 1, after being converted to a digital signal at an A/D converter 2, is written on a memory 3. A picture data read out from the memory 3 is compressed and encoded with high efficiency at a compressing stretching circuit 4, and applied with phase-modulation or an orthogonally modulation analog signal at a modem 5. The output of the modem 5 receives a band limitation from f2 to f3 at a band pass filter BPF6, and is inputted to a mixing circuit MIX13. Meanwhile, a sound, after being converted to a sound electrical signal with a microphone 9, is sent to a low-pass filter 12 through an amplifier AMP11, and is band-limited below F2, then being inputted to the mixing circuit 13. The mixing circuit 13 mixes the picture signal from the band-pass filter BPF6, with the sound signal from the low-pass filter LPF12, and out-puts a mixing signal of the picture signal and the sound signal to the telephone line connected to a terminal 20.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a transmission system for transmitting television images and sounds via a telephone line.

(Prior Art) Conventionally, a so-called still image transmission device that transmits television images using a narrowband transmission path such as a telephone line, as shown in Japanese Patent Application No. 50-48305, It was a method for transmitting still images using bandwidth.

(Problems to be Solved by the Invention) The above-described conventional silent image transmission device exclusively uses one telephone line. Therefore, if audio is to be transmitted in addition to still images, one telephone line is required in addition to one line for still images, and a total of two lines must be provided. This is because a band of about 3000 Hz is normally required to transmit human voice, so one line must be allocated for voice as well. However, when a hearing-impaired person uses an image transmission device, the audio band must be 300.
0 Hz is not required. From individual experimental results, even for people with moderate hearing loss, the to00HzcD hearing loss is approximately 60 d.
This is approximately 90 dB for advanced pheasant listeners.

However, this is not to say that audio is not required at all in the image transmission used by hearing-impaired people; it has been found that it responds to certain frequencies, for example, the sound of a person on the screen. Even when reading lip movements, L
Audio information below OOOH2 plays an important role. In view of these circumstances, it is an object of the present invention to provide an information transmission system that allows audio signals and image signals to be transmitted simultaneously over a single line.

(Means for Solving the Problems) Means provided by the present invention to solve the problems described in Moe's text is a method of transmitting information via a telephone line, in which audio signals are transmitted from fl to ft (0 < ft < ft), and a low-pass filter that limits the frequency band to f
t<fs), and mixes the audio signal whose band is limited by the low-pass filter and the image signal whose band is limited by the band filter. and a mixing circuit for transmitting signals to the telephone line, and the frequency f is below the frequency band of the telephone line.

(Embodiments) First, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a system diagram of an embodiment of the present invention. In this embodiment:A, a television signal imaged by a chimp camera 1 is converted into a digital signal by an A/V converter 2 and then written to a memory 3. The memory 3 is for converting the time axis according to the band of the line, and its update time changes according to the compression ratio of the next compression/expansion circuit 4. For example, in the still image mode, the update time is approximately once every 30 seconds, and in the moving image mode, the update time is approximately once every λ to 10 seconds. The image data read from the memory 3 is compressed and encoded with high efficiency by a compression/expansion circuit 4, and converted into an analog signal subjected to phase modulation or quadrature modulation by a modem 5. The output of the modem 5 is subjected to band restriction from f to f by a bandpass filter 3 (BPF) 6 and input to a mixing circuit (MIX) 13.

On the other hand, the audio is converted into an audio electrical signal by microphone 9 and then amplified! (AMP)LL is sent to the low-pass filter L2 via L2, where it is band-limited as follows and input to the mixing circuit 13. The mixing circuit 13 includes a bandpass filter 6 (BPF) 6
The image signal from the low-pass filter 5 (LPF) 12 is mixed with the audio signal from the low-pass filter 5 (LPF) 12, and a mixed signal of the image signal and the audio signal is output to the telephone line connected to the terminal 20.

FIG. 2 shows the frequency spectrum of the signal output from the embodiment of FIG. 1 to the telephone line. The low frequency band intervention in FIG. 2 is the audio signal channel, and the high frequency band B is the image signal channel.

Although the transmitting function has been described above, the embodiment shown in FIG. 1 also has a receiving function as described below.

The equalization signal received at the terminal 20 is sent to the bandpass filter 6 after passing through the mixing circuit 13, and the passband f in the bandpass filter 6 is
An image signal is selected by twf. The selected image signal is supplied to the modem 5, demodulated, expanded by the pressure 2a expansion circuit 4, and loaded into the memory 3. Image information is constantly read out from the memory 3 at a television scan rate so that it can be displayed on a monitor 8, and is sent out as an image signal.

The image signal output from the memory 3 is a digital signal, and this digital signal is converted into an analog signal by the D/A converter 7 and displayed as an image on the television monitor 8.

Among the signals received at the terminal 20, the signal in the band from fl to f is selected as an audio signal component by a low-pass filter 512, and this audio signal component is amplified by an amplifier 11, and then converted from an electrical signal to audio by a speaker 10. converted.

In addition, in FIG.
3 are shown as bidirectional, but it is obvious that they can also be configured as a unidirectional combination.

In addition, the data rate that can be transmitted on the high-frequency channel in Figure 2 is approximately 1200 bits/second (f), which is equivalent to L800HzlCA, and with this level of data transmission rate, it is not only possible to send still images, but also to send images of lips. Videos that convey movement can be sufficiently transmitted.

In the present invention, f@m fly f@ does not need to be particularly limited as long as it has the magnitude relationship shown in FIG. 2 (however, f.

(is equal to or smaller than the transmission frequency band of the telephone line), and from a practical standpoint, it is realistic to select values near 300H3,f, 1800Hz, and f3 near 3400Hz.

(Effect of the invention) As explained above, the information transmission method of the present invention
It divides the Hz frequency band and transmits audio signals in the low range and image signals in the high range. Therefore, according to the present invention, it is possible to provide an information transmission system that can simultaneously transmit image and audio information using a single telephone line.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing one embodiment of the present invention, and Fig. 2 is a system diagram showing an embodiment of the present invention.
FIG. 3 is a diagram showing a frequency spectrum of a transmission signal on a telephone line connected to the illustrated embodiment. 1...TV camera, 2...A/D converter, 3
...Memory, 4...Compression/expansion circuit, 5...Modem, 6...Band filter, 7...D/A converter, 8
...TV monitor, 9...Microphone, 10...Speaker, 11...Additional equipment, 12...Low-pass filter, 1
3...Mixing circuit, 20...Terminal.

Claims (1)

[Claims] In a system for transmitting information via a telephone line, a low-pass filter limits audio signals to a frequency band from f_1 to f_2 (0≦f_1<f_2), and a low-pass filter limits image signals to a frequency band from f_2 to f_2.
a bandpass filter that limits the frequency band to a frequency band of _3 (f_2<f_3), the audio signal whose band is limited by the low-pass filter, and the image signal whose band is limited by the bandpass filter. An information transmission system comprising: a mixing circuit that mixes and sends the mixture to the telephone line, and the frequency f_3 is below the frequency band of the telephone line.