[Description of the Prior Art] There are several types of methods for visual telecommunication such as a method of using an international mobile telecommunications-2000 (IMT-2000), a method of using an IP network, and a method of using PSTN.

The method of using an IMT-2000 is based on the standard established by ITU and provides a high frequency band (2GHz) and a wide bandwidth (2Mb).

However, it is not fully serviceable yet due to various technical and/or economical problems.

The methods of visual telecommunication using a wired transmission can be basically classified into a method

of using an IP network and a method of using PSTN.

In case of a method of using an IP network, it performs a visual telecommunication on Internet by using H. 323, an ITU standard recommendation.

And in case of a method of using PSTN, it performs a visual telecommunication on general telephone network by using H. 324, an ITU standard recommendation.

FIG. 1 is a block diagram illustrating the structure of a conventional wired videophone using PSTN.

As described in FIG. 1, a wired videophone (10) comprises: a telephone line section (11) that is connected to a terminal of the other party through PSTN (9); a logic section B (12), connected to telephone line section (11), that modulates/demodulates the video and audio signals; a camera section (13) that photographs the images and transmits them to logic section B (12); a display section (14) that displays the video signals processed by logic section B (12); a keypad section (15) that receives input key-values and transmits them to logic section B (12); and a transmitting/receiving section (16) comprising a speaker section (18) that outputs the audio signals processed by logic section B (12) and a microphone section (17) that receives audio inputs and transmits them to logic section B (12).

In a wired videophone (10) having the structure described above, the terminal itself modulates/demodulates the audio and video signals and communicates the signals with another terminal of the other party through PSTN (9) to carry out a visual telecommunication.

However, a wired videophone (10) described above has a disadvantage in usability since the terminal should be fixed at PSTN (9) or an IP network.

On the other hand, a prior application of KR 10-1999- 047307 (a wired/wireless compatible videophone using a mobile videophone) discloses a technology of a videophone comprising: a mobile section that performs a wireless visual telecommunication by transmitting/receiving data to/from a mobile video terminal of the other party through wireless transmission network and modulating/demodulating the audio and video signals into digital signals or vice versa; and a fixed section, designed to be connected to the mobile section, that performs a visual telecommunication by transmitting/receiving data to/from a wired video terminal of the other party through wired telephone network and modulating/demodulating the audio and video signals.

So, by using a mobile videophone like an IMT-2000

terminal, each section can be separately operated as a mobile videophone and a wired telephone when they are separated, and it performs the function of audio/video input/output of a mobile videophone and the function of audio/video signal processing of a wired telephone compatibly when the sections are connected to each other.

However, the prior application described above is claiming for a combined use of a mobile videophone and a wired videophone. And it has a problem that, in case of using a wired telephone network, the mobile section and the fixed section have to be wired to each other.

[Description of the Invention] The present invention is proposed to solve the problems of usability of the prior art mentioned above.

It is therefore the object of the present invention to provide a cordless videophone that can transmit/receive the visual telecommunication data through PSTN using a wireless terminal.

It is another object of the present invention to provide a cordless videophone that can transmit/receive the visual telecommunication data through an IP network using a wireless terminal.

To achieve the object mentioned above, the present invention presents a cordless videophone comprising: a fixed station that is connected to PSTN or an IP network to transmit/receive audio and video data to/from the other party and wirelessly transmits/receives these data to/from a wireless terminal; and a wireless terminal that separates the data into audio signals and video signals and modulates/demodulates these signals for carrying out a visual telecommunication.

The present invention also presents a cordless videophone comprising: a fixed station that is connected to PSTN or an IP network to transmit/receive audio and video data to/from the other party, separates the data into audio signals and video signals, modulates/demodulates these signals, and wirelessly transmits/receives these signals to/from a wireless terminal; and a wireless terminal that transmits/receives the audio and video signals for carrying out a visual telecommunication.

[Brief Description of the Drawings] FIG. 1 is a block diagram illustrating the structure of a conventional wired videophone using PSTN.

FIG. 2 is a block diagram illustrating the structure of a cordless videophone using PSTN in accordance with the present invention.

FIG. 3 is a block diagram illustrating the structure of a cordless videophone using an IP network in accordance with the present invention.

[Detailed Description of the Embodiments] Hereinafter, referring to appended drawings, the structures and the operation procedures of the embodiments of the present invention are described in detail.

Looking into the basic structure of the present invention, the present invention comprises: a fixed station (30 or 40) that is connected to PSTN (9) or an IP network (8) to transmit/receive audio and video data to/from the other party and wirelessly transmits/receives these data to/from a wireless terminal (20); and a wireless terminal (20) that separates/combine the data into/from audio signals and video signals and modulates/demodulates these signals for carrying out a visual telecommunication.

Referring to FIG. 2, an embodiment of the cordless videophone (A) in accordance with the present invention

comprises a fixed station (30) wired to PSTN (9) and a wireless terminal (20) wirelessly communicating with the fixed station (30).

The fixed station (30) comprises a telephone line section (31) connected to PSTN (9) for data transmission/reception, a charging section (33) designed to be connected to power supply section (28) of a wireless terminal (20) for supplying electric power to the wireless terminal (20), a keypad section (35) that receives input key-values and transfers them to logic section A (32), and an RF section (34) that modulates/demodulates the signals for the communication with the wireless terminal (20).

The fixed station (30) further comprises a logic section A (32) that processes the key-values received by the keypad section (35), controls the charging section (33), communicates with PC (36), processes the data received from the telephone line section (31) and the RF section (34), and connects them to each other.

A wireless terminal (20) comprises an RF section (21) that modulates/demodulates the signals for the communication with a fixed station (30), a logic section B (22), connected to RF section (21), that compresses digitized audio and video signals or vice versa and transmits/receives them, a power supply

section (28) designed to be connected to the charging section (33) of the fixed station (30) for supplying electric power to the wireless terminal (20), a camera section (23) that photographs images and transmits them to logic section B (22), a display section (24) that displays the images reconstructed by logic section B (22), a keypad section (25) that receives input key- values and transfers them to logic section B (22), a microphone section (26) that receives audio inputs and transfers them to logic section B (22), and a speaker section (27) that outputs the audio signals processed by logic section B (22).

Another embodiment of the cordless videophone (A) in accordance with the present invention comprises a fixed station (40) wired to an IP network (8) and a wireless terminal (20) wirelessly communicating with the fixed station (40).

The fixed station (40) comprises a network line section (41) connected to an IP network (8) for data transmission/reception, a charging section (43) designed to be connected to power supply section (28) of a wireless terminal (20) for supplying electric power to the wireless terminal (20), a keypad section (45) that receives input key-values and transfers them to logic section A (42), and an RF

section (44) that modulates/demodulates the signals for the communication with the wireless terminal (20).

The fixed station (40) further comprises a logic section A (42) that processes the key-values received by the keypad section (45), controls the charging section (43), communicates with PC (46), processes the data received from the network line section (41) and the RF section (44), and connects them to each other.

A wireless terminal (20) comprises an RF section (21) that modulates/demodulates the signals for the communication with a fixed station (40), a logic section B (22), connected to RF section (21), that compresses digitized audio and video or vice versa and transmits/receives them, a power supply section (28) designed to be connected to the charging section (43) of the fixed station (40) for supplying electric power to the wireless terminal (20), a camera section (23) that photographs images and transmits them to logic section B (22), a display section (24) that displays the images reconstructed by logic section B (22), a keypad section (25) that receives input key-values and transfers them to logic section B (22), a microphone section (26) that receives audio inputs and transfers them to logic section B (22), and a speaker section (27) that outputs the audio signals processed by logic

section B (22).

Even though the fixed station (30) of a cordless videophone (A) is connected to PSTN (9) in the embodiment described in FIG. 2 and the fixed station(40) of a cordless videophone(A) is connected to an IP network(8) in the embodiment described in FIG.

3, a cordless videophone (A) in accordance with the present invention can be operated in both cases.

These applicability depends on how to construct the logic section A's (32,42) and the logic section B (22).

In addition, the digitization and reconstruction of data, performed by logic section B (22) in FIG. 2 and FIG. 3, can be performed by logic section A's (32,42) instead.

Furthermore, depending on the constitutions of logic section B (22) and logic section A's (32,42), the digitization and reconstruction of data can be partially performed by logic section B (22) and logic section A's (32,42) respectively.

With the structure described thereinbefore, the present invention provides a cordless videophone'using the conventional PSTN (9) or an IP network (8) but using a wireless terminal (20). And thus, it provides a convenient usability.

In addition, it provides the function of a

conventional audio-telephone as well as a visual telecommunication to maintain the compatibility with a conventional telephone.

In other words, with the operation procedures similar to that of a conventional cordless telephone, the present invention provides an additional function of visual telecommunication.

Visual telecommunication can be carried out by initially setting a video option when making a phone call, or it can be switched from audio telecommunication during the communication.

The power supply section (28) of a wireless terminal (20) is charged through the charging sections (33,43) of fixed stations (30,40), and the fixed stations (30,40) are operated by the communication with PCs (36,46) through logic section A's (32,42).

Since those having ordinary knowledge and skill in the art of the present invention will recognize additional modifications and applications within the scope thereof, the present invention is not limited to the embodiments and drawings described above.

In other words, the present invention is based on the upcoming mobile videophone and the conventional wired

videophone. Therefore, it is also applicable to a visual telecommunication based on a modem communication, a cable modem communication, or an asymmetric digital subscriber line (ADSL) technology on wired circumstances.

[Industrial Applicability] As mentioned thereinbefore, a cordless videophone in accordance with the present invention increases its usability and provides the convenience of mobile visual telecommunication within a certain range by making a wireless visual telecommunication possible.