1. Field of the Invention
The present invention relates to a communication line connecting adapter which connects a public telephone line, an extension line (an internal lines), Voice over Internet Protocol (VoIP) gateway and a modem/facsimile machine.
2. Description of the Related Art
With the progress of the Internet technology, telephone communication using the Internet (so-called IP phone) is becoming popular.
The telephone communication over the Internet uses a protocol, such as H.323 or Session Initiation Protocol (SIP).
The following describes some modes of the telephone communication over the Internet.
A local area exchanger connected to a public telephone line is connected to a VoIP gateway which is connected to a local area IP network (such as Local Area Network(LAN) and Wide Area Network(WAN)), and another VoIP gateway is connected to the local area IP network. Ordinary telephones are connected to each VoIP gateway. This connection can allow the extensions (internal lines) in a company to be constructed by an IP network and eliminates the need for constructing the extensions by a telephone network. However, to connect an extension to an outside line, a public telephone line should be used. This is a local area telephone communication over the Internet.
On the other hand, each VoIP gateway is connected to each router connected to the Internet (global IP network) and an ordinary telephone is connected to each VoIP gateway directly or via an extension line. This connection eliminates the need for a public telephone line to communicate with an outside line, therefore this connection leads to a reduction in a telephone charge. This is a WAN telephone communication over the Internet.
The “VoIP gateway” mainly converts an analog voice signal to digital voice data, divides the digitized voice data and triply encapsulates the divided digital data by using a Real-Time Transport Protocol (RTP) packet, an User Datagram Protocol (UDP) packet and an Internet Protocol (IP) packet in communication in one direction, and further extracts digitized voice data from an IP packet and converts the extracted voice data to an analog voice signal in communication in the other direction.
The following are the prior art documents relating to the present invention.
Patent Document 1: JP-A-1991-135148
Patent Document 2: JP-A-1993-14583
Patent Document 3: JP-A-1993-68118
Patent Document 4: JP-A-2000-354071
Patent Document 5: JP-A-2001-186193
Patent Document 6: JP-A-2001-298542
The invention disclosed in the Patent Document 1 can enable data communication of data terminals with each other without redialing by connecting multifunction telephone terminals and data terminals to each line circuit and pressing a predetermined button on one multifunction telephone terminal while the multifunction telephone terminal is communicating with another multifunction telephone terminal. This invention allows talking and data communication using the same line.
In the invention disclosed in Patent Document 2, immediately after a line is closed, a guidance voice message is sent and a selector circuit is switched to the modem side, transmission of a called terminal identification signal CED and digital identification signal DIS and detection of a digital command signal DCS are repeated, and facsimile reception is started if the digital command signal DCS is detected during the repetitive operation and the selector circuit is switched to the telephone side to start talking if off-hook is detected during the repetitive operation. As this invention causes a communicating party to wait for the process to be switched while a guidance voice message is sent and, the operability for the communicating party is not high. Even while process switching is being monitored, talking can begin soon in case that a communication station side (an other end of the line) is a telephone, but facsimile communication cannot be started or continued unless the telephone is on-hooked again, if telephone is once off-hooked, in case that the communication station side (the other end of the line) is a facsimile.
In the invention disclosed in Patent Document 3, a calling tone CNG from a communication station side (an other end of the line) or an off-hooking on own station side is waited while ringing a quasi ringback tone until a predetermined time elapses after closing of a line.
If the calling tone CNG is firstly detected in the predetermined time, a sequence associated with a predetermined called terminal identification signal CED, digital identification signal DIS and digital command signal DCS for facsimile reception is started and if off-hooking is firstly detected in the predetermined time, talking starts. On the other hand, if neither the calling tone CNG nor off-hooking is detected in the predetermined time, the sequence associated with the predetermined called terminal identification signal CED, digital identification signal DIS and digital command signal DCS for facsimile reception is started.
In the invention disclosed in Patent Document 4, WAN telephone communication over the Internet is generally performed and the WAN telephone communication is switched to the mode using a public telephone line when the quality of the WAN telephone communication is degraded.
The invention disclosed in Patent Document 5 relates to a VoIP gateway that is used in the aforementioned WAN telephone communication over the Internet.
The invention disclosed in Patent Document 6 can ensure that a received call from an outside line is transferred to an existing extension telephone network and network simultaneously used and can permit a response to a telephone call from an outside line received even when a failure occurs.
In a local area telephone communication over the Internet, a public telephone network is connected to a VoIP gateway. However, a facsimile machine and a modem may further be connected to the public telephone network. There was no prior art technique which would cope with how to control the connection in case where a VoIP gateway, a facsimile machine and a modem are connected to a public telephone network.
At present, ordinary telephones and IP phones coexist. Because one of an ordinary telephone and IP phone is used in the local area and one of the ordinary telephone and IP phone is used on the talking party side, there are four kinds of connections possible. However, there was no prior art technique which would cope with all of the four kinds of connections.
In case that a user owns an IP phone, it is likely that there is a growing demand of receiving not only a call for the IP phone but also a call for an ordinary telephone by using the IP phone.