Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1999-12-21
2003-07-15
Patel, Ajit (Department: 2664)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S410000
Reexamination Certificate
active
06594256
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication apparatus and, more particularly, to a communication apparatus for transferring dual tone multi-frequency (DTMF) signals, facsimile answer tone signals, etc. in performing communication by using packeted sound signals.
2. Description of the Related Art
Integration of a speech network such as a telephony network and a signal network such as a LAN has been achieved by the Internet or other wide-area computer networks, and is being put in practical use as an Internet telephone service. The Internet is based on packet switching. Each packet selectively passes through a plurality of computers and networks by routing until it reaches its target counterpart.
The Internet has been achieving its development based mainly on protocols generally referred to as transmission control protocol/Internet protocol (TCP/IP), the Internet protocol (IP) being the core. The IP is a connectionless protocol based on a signal program, and guarantees nothing about the time required for signals to reach or sequence of signals. In the TCP/IP, therefore, a transport protocol class is specified separately from the IP. The transport protocols of the TCP/IP include a transmission control protocol (TCP) and a user datagram protocol (UDP). The TCP is a connection type protocol for accomplishing highly reliable byte stream transfer, and finds its applications in transfer of mail or files, remote login protocols, etc. The UDP is a low-reliability datagram protocol and does not guarantee perfection. On the other hand, the UDP permits flexible, highly efficient signal transfer for some applications or network environments because it requires no virtual circuit to be established and involves no fixed paths for signal transfer.
The Internet is generally configured by first configuring a local area network (LAN) in a company, then connecting the LAN to the Internet. Normally, when using the Internet or a network such as a LAN and packeting speeches to perform communication, sound signals are converted into UDP packets and sent out onto a channel for call of a network. Control signals are converted into TCP packets and sent out onto a channel for control of the network.
Regarding DTMF signal transfer, the ITU-T Recommendation H. 245 specified a method for converting DTMF signals into TCP packets and sending them out onto a channel for control.
The DTMF signals, however, are transferred through the channel for control and also passed as sound signals through a channel for speech at the same time. A receiver, therefore, receives the DTMF signals from both the channel for control and the channel for speech, causing erroneous detection to take place.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to achieve reliable transfer of DTMF signals by preventing the DTMF signals from being doubly received by a receiver due to the DTMF signals being transferred as sound signals to the receiver through a channel for call when transferring the DTMF signals through a channel for control.
To this end, according to one aspect of the present invention, there is provided a communication apparatus for sending out a first signal included in an input signal onto a channel for call and sending out a second signal included in the input signal onto a channel for control, the communication apparatus comprising: a first signal transmitting module that temporarily stores the input signal and transmits the input signal onto the channel for call; a second signal transmitting module that transmits a signal supplied to an input terminal onto the channel for control; an FIFO control module that deletes the second signal already stored in the first signal transmitting module when a signal is supplied to the input terminal; and a signal control module that detects whether the input signal is the second signal or not, transmits a third signal that corresponds to silence to the first signal transmitting module in place of the input signal while detection of the second signal is being implemented, and transmits the second signal to the input terminal when the second signal has been detected.
The signal control module comprises a signal detective module that detects whether the input signal is the second signal or not, sends out an instruction signal and also transmits the second signal to the second signal transmitting module and the FIFO control module when the second signal has been detected, and sends out the instruction signal again when the detection of the second signal is completed; a third signal generating module that generates the third signal that corresponds to silence; and a third signal control module that carries out control so that the third signal is transmitted to the first signal transmitting module in place of the input signal until the instruction signal is received again after the instruction signal is first received.
The third signal control module cuts off a first channel that leads the input signal to the first signal transmitting module, and connects a second channel to the first signal transmitting module from the third signal generating module to thereby conduct control so that the third signal is transmitted in place of the input signal to the second signal transmitting module.
The first signal transmitting module comprises a signal compressing module that compresses the input signal and outputs the compressed signal, a UDP packet control module that converts the compressed signal into a UDP packet and outputs the UDP packet, and an FIFO that stores the UDP packet as the input signal for a predetermined time before transmitting it to the channel for call.
The second signal transmitting module converts the second signal into a TCP packet and transmits the converted second signal to the channel for control.
The FIFO control module goes back for a predetermined time from a point where a signal was supplied to the input terminal, and deletes the second signal already stored in the first signal transmitting module.
The predetermined time means an adequate time that has been set by taking into account a delay time in processing by the communication apparatus and that is sufficiently long to delete the second signal already stored in the first signal transmitting module. Furthermore, the predetermined time means a time during which the input signal is sent out from a terminal connected to the communication apparatus and the second signal is supplied to the input terminal.
According to another aspect of the present invention, there is provided a communication apparatus for sending out a first signal included in an input signal onto a channel for call and sending out a second signal included in the input signal onto a channel for control, the communication apparatus comprising: a signal compressing module that compresses the input signal and outputs the compressed signal; a UDP packet control module that converts the compressed signal into a UDP packet and outputs the UDP packet; an FIFO that stores the UDP packet as the input signal for a predetermined time, then transmits the UDP packet to the channel for call; a TCP packet control module that converts the second signal into a TCP packet and transmits the converted second signal to the channel for control; an FIFO control module that deletes the second signal already stored in the first signal transmitting module when a signal is supplied to the input terminal; a signal detective module that detects whether the input signal is the second signal or not and sends out an instruction signal and also transmits the second signal to the TCP packet control module and the FIFO control module when the second signal has been detected, and sends out an instruction signal again when the detection of the second signal is completed; a silence generating module that generates a signal corresponding to a silence; and a silence sending module that carries out control so that the signal corresponding to silence is transmitted, in place of the input signal, to the signal com
Jain Raj
Oki Electric Industry Co. Ltd.
Patel Ajit
Rabin & Berdo P.C.
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