JPH01258574A - Videophone device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to videophones, and particularly to the transmission of image signals and audio signals.

[Prior art]

FIG. 8 shows an example of a conventional video telephone device. When used as a normal telephone, the telephone P is connected to a public analog telephone line T by switching the switch SW to the telephone side.

When performing image communication, when an operation unit (not shown) is operated to instruct image communication, the switch SW is switched, and the public analog telephone line T is connected to this switch SW.
It is connected to modem M via.

In this state, an image to be transmitted is captured by an imaging means C such as a television camera, and its output signal is converted into a predetermined image signal by an image processing section S, and then the modem M
, and is sent out to the public analog telephone line T via the switch sW.

The image signal from the other party is sent from the public analog telephone line T to the image processing section R on the receiving side via the switch S'vV and modem M, and is displayed on an image output section such as a CRT display device. Ru.

Then, when making a call with the other party, use the above switch SW.
After connecting the public analog telephone line T to the telephone set P, the telephone call is made in the same manner as in the above-mentioned normal telephone call.

Therefore, in such conventional technology, there was a problem in that image transmission and audio transmission could not be performed simultaneously.

〔the purpose〕

An object of the present invention is to enable image and audio signals to be transmitted and received simultaneously even when used as a videophone.

〔composition〕

In order to achieve the above object, the present invention is characterized in that an image signal modulated by a modem and an audio signal are superimposed and transmitted.

Hereinafter, the present invention will be specifically explained based on examples. Note that corresponding components in each of the following embodiments are given the same reference numerals, and components corresponding to those in the conventional example described in FIG. 8 are referred to as those in FIG. The same reference numerals are given.

FIG. 1 shows a first embodiment of the present invention.
The public analog telephone line T is constantly connected to a high-pass filter HF and a low-pass filter LF at the connection point, and image signals are transmitted and received between the modem M and the public analog telephone line T via the high-pass filter HF, and audio signals are It is configured to be transmitted and received between the telephone P and the public analog telephone line T via a low-pass filter LF.

That is, the voice signal from or to the telephone P is transmitted and received in a low frequency band determined by the cutoff frequency of the low-pass filter LF, and the modulated image signal from or to the modem M is transmitted and received at the cutoff frequency of the high-pass filter HF. It is transmitted and received using a high frequency band determined by

Image information to be transmitted from an image input unit C such as a television camera is converted by an image signal processing unit S into a digitally encoded image signal that conforms to the transmission and reception standards, and then is converted into a digitally encoded image signal that conforms to the transmission and reception standards, for example, according to the “CCITT Recommendation V27 ter” standard. Modem M
The signal is modulated into a 2.400bps transmission signal.

The frequency band of the image signal modulated by this modem is
As shown in the figure, since the image signal has a band of 1 Hz or more, this image signal can be transmitted and received through a high-pass filter HF with a cutoff frequency of I kHz.

When receiving image signals, as in the case of transmission above,
The image signal from the public analog telephone line T is input to the modem M through a high-pass filter HF, where it is demodulated into a digitally encoded image signal, and the image output section outputs the signals necessary to display it as an image. After being converted by the image processing unit R on the receiving side, the received image is displayed by the image output ND.

On the other hand, the audio signal is transmitted and received via the low-pass filter LP, which has a cutoff frequency of I KHz, which is equal to the cutoff frequency of the above-mentioned high-pass filter, so only the audio frequency components below I KHz are transmitted. Transmission and reception are performed in a frequency band narrower than the transmission frequency band of the telephone line, and although the sound quality deteriorates somewhat, it does not interfere with normal conversation.

Instead of modulating a signal with a transmission rate of 2.400 bps using the above-mentioned "CCITT Recommendation V27ter" modem, a "CCITT Recommendation V29" standard modem modulates the signal with a transmission rate of 9.
When the present invention is implemented at a transmission speed of 600 bps, the frequency band of the image signal modulated by this modem becomes a band of 400 Hz or more, as shown in FIG. 4, so the frequency band that can be used for audio transmission is 0. ~400Hz, and although the sound quality is worse than in the above case, it is sufficient to convey the intentions of the caller.

At this time, a high-pass filter H for image signal transmission is used.
It goes without saying that the cutoff frequencies of F and the low-pass filter LF for audio signal transmission are both 4001 (z).

FIG. 2 shows a second embodiment of the present invention, in which the transmission and reception of image signals is cut off by a switch SWO when making a normal phone call using only voice, thereby eliminating unnecessary noise patterns from the image output section. This prevents it from being played. Note that this switch SWo is connected to the image input section C1 and the image processing section S.
, R, the image output section, and the modem M may be opened and closed in conjunction with the supply of operating power.

In the first and second embodiments described above, there is a drawback that the sound transmitted and received by the telephone is always subject to high-frequency attenuation by the low-pass filter LF, resulting in deterioration of sound quality.

In order to eliminate this drawback, Fig. 3 shows a system in which a means is provided to prevent the voice signal from passing through the low-pass filter LF when used as a normal telephone. When making a call, switch to the telephone mode by switching the first and second switches SW+ and SW2, which are provided to switch between the telephone mode and the videophone mode, to the contact a side. The telephone IMP is directly connected to the public analog line, and a call can be made using the entire frequency band that can be transmitted and received as a normal telephone without being affected by the low-pass filter LF.

When used as a videophone, the videophone mode is set by switching both the first and second switches SW1 and SW2 to the contact side. This embodiment has the same configuration as the first embodiment, and therefore performs the same operation, but since the operation has been explained previously, the explanation thereof will be omitted.

FIG. 5 shows another embodiment according to the present invention,
For example, with a modem that complies with the "CCITT Recommendation V27ter" standard, the frequency band of the image signal modulated by the modem modulates into a 2.400 bps transmission signal is approximately I
By taking advantage of the fact that it is in the range of Khz to 3 Khz, and using the frequency bands above and below the output frequency band of this modem for audio signal transmission, it is possible to transmit even better quality audio. Components corresponding to those of the embodiments described above are given the same reference numerals, and their explanations will be omitted.

In this embodiment, when used as a videophone, a band converter FS and a high-pass filter SHF for audio are connected in parallel to the low-pass filter LF for limiting the high frequency band of audio components in the embodiment shown in FIG. At the same time, the output of modem M is connected to bandpass filter BF.
, and then superimposed on the outputs of the filters LF and SHF.

Figure 6 shows the bandpass characteristics of the filters LF, SHF, and BF.
KHz, and the passband of the high-pass filter SHF is 3 KHz or more, as indicated by "C". The passband of the bandpass filter BF provided in the transmission path of the image signal modulated by the modem is the same as that of the bypass filter SHF and the low-pass filter LF, as shown by "b".
occupies the middle gap in the passband of I KHz ~ 3 KH
It is z.

FIG. 7 schematically shows the transmission state of the audio signal in this embodiment. When the caller instructs to use the videophone, the transmission request detector ED detects this instruction and the first and second 2nd relay RyI, R)'2 to 5th relay
As shown in the figure, the contact position is switched to the b side, and an identification tone of, for example, 2.100 Hz is sent to the receiving side, and the receiving side, which has the same configuration as the sending side, detects this identification tone with a tone detector TD. The above relay Ry+, Ry
The relay corresponding to z is automatically switched to the contact position on the b side, similar to the sending side.

Figure 7(a) shows O input from a telephone (handset).
The audio signal is exemplified as Hz to 5 KHz, and is sent to the band converter FS via the relay Ry+, where the band converter FS modulates the 2 KHz carrier wave, so that the audio signal is converted into the signal as shown in the figure. 2K)l
z to 7 KHz frequency band.

This band-converted audio signal is passed through the bypass filter S.
By passing the HF, only the high-frequency audio signals in the frequency band of 3 KHz or higher, that is, the high-frequency audio signals in the frequency band of I KHz or higher before frequency conversion, are bypassed, as shown in Figure (C). Filter SHF
output from.

On the other hand, the low-frequency audio signal below I KHz passes through the low-pass filter LF, and the image signal modulated by the modem M passes through the band-pass filter BPF, respectively.
At point Ao, which is the input terminal of relay Ry+ in the figure, it is superimposed on the output of the bypass filter SHF, and
By the frequency arrangement shown in d), the relay Ry
It is sent out to the public analog telephone line T via the + contact.

A fifth telephone having the same configuration as the transmitting side which received the signal as shown in FIG. 7(d) above from the public analog telephone line T.
In the receiving side device shown in the figure, the relays Ryl and Ry2 are also switched to the same position as the transmitting side as described above, so the modulated image signal is transferred to the relay Ry+.
Band pass filter BF is applied from point “Ao” which is the output point of
The signal is then sent to the modem M, demodulated, and reproduced as an image from the image processing section R by an image output section such as a cathode ray tube display.

On the other hand, the high-frequency audio signal whose band has been converted as described above is inputted from the above point "A" through the bypass filter SHF to the band converter FS and returns to the original frequency as shown in FIG. 7(e). It is returned to the frequency band and is superimposed with the low-frequency audio signal that has passed through the low-pass filter LF, as shown in (f) in the same figure.
It is supplied to the telephone as an audio signal substantially the same as the output signal from the transmitting telephone in a).

When the transmitter ends the use as a videophone or performs telephone communication, the transmission request detector ED does not receive an instruction from the caller to use the videophone, so the above-mentioned first and Second relay RY +, R
y2 is switched to the contact "a" side.

As a result, the telephone is directly connected to the public analog telephone line T via these relays Ry, Ry2, and transmits and receives only voice signals, but at this time, the entire frequency band of the public analog telephone line is used for voice transmission. It goes without saying that there is no need to perform the above processing.

Note that this example describes the case where a modem compliant with the "CCITT Recommendation V27ter" standard is used;
It is clear that the application can also be applied to the case of a transmission speed of In the embodiment shown in FIG. 5, the frequency band that can be used for audio transmission is from 0 to 400 Hz, resulting in a significant deterioration of the audio. However, according to the embodiment shown in FIG. Since it can be used to transmit audio signals, it is possible to reduce audio deterioration.

〔effect〕

According to the present invention, it is possible to achieve the special effect that audio can be transmitted and received even while an image signal is being transmitted, and images can be transmitted and received even while an audio signal is being transmitted.

[Brief explanation of the drawing]

Figures 1 to 3 are block diagrams showing embodiments of the present invention, Figure 4 is a diagram showing the frequency band of the image signal modulated by the modem, and Figure 5 is a diagram showing another embodiment of the present invention. 6 is a block diagram showing the pass band of the filter used in this embodiment, FIG. 7 is a diagram schematically showing the transmission state of the audio signal in this embodiment, and FIG. 8 is a diagram showing a conventional TV. 1 is a block diagram showing a telephone; FIG. Patent Applicant Ricoh Co., Ltd. -] 4 castle teaching area children's words 4 instruments shielding several thousand 8゛Fig.

Claims (1)

[Claims] (1) A video telephone system characterized in that an image signal modulated by a modem and an audio signal are superimposed and transmitted in different frequency bands. (2) The videophone system according to claim 1, characterized in that an image signal modulated by a modem that has passed through a high-pass filter and an audio signal that has passed through a low-pass filter are superimposed and transmitted. (3) Divide the audio signal into a low-frequency audio signal and a high-frequency audio signal according to the lower limit frequency of the image signal band modulated by the modem, and convert this high-frequency audio signal into an image signal whose lower limit frequency is modulated by the modem. A video telephone system characterized in that the frequency band is converted to the upper limit frequency of the band, and then the image signal and the low-frequency audio signal modulated by the modem are superimposed and transmitted. (4) The videophone system according to claim 3, wherein when used as a videophone, an identification tone is transmitted from the transmitting side to the receiving side to switch the transmission/reception mode.