Backup apparatus against line defect and backup method against line defect

A backup apparatus against a line defect for use in a communication system having a multi-point connection for transferring data between a host unit and a plurality of terminal units through a modem via an analog line, said backup apparatus comprising:

• an ISDN interface portion for transmitting and receiving a digital signal over an ISDN line;
• two A/D converting portions, referred to as a first A/D converting portion and a second A/D converting portion, each for receiving a first analog signal from said modem connected to said host unit, each for converting the first analog signal into a first digital signal synchronized with a timing of the ISDN line, and each for supplying the synchronized digital signal to said ISDN line through a respective channel in said ISDN interface portion;
• two D/A converting portions, referred to as a first D/A converting portion and a second D/A converting portion, each for receiving a third and a fourth digital signal from said ISDN line through a respective channel in said ISDN interface portion, each for converting the third and fourth digital signal into a respective third and fourth analog signal, and each for supplying the third and fourth analog signal to said modem;
• and
• a controller portion which controls said modem to connect with said analog line to transmit and receive data over said analog line when said analog line is functioning properly and which controls said ISDN interface portion to transfer to said ISDN line from said host unit a channel data of digital signals which are received from said first and second A/D converting portions and to supply to said modem two analog signals from data transmitted over said ISDN line from said plurality of terminal units and converted by said first and second D/A converting portions when a defect occurs over said analog line.

A backup apparatus against line defect for use in a communication system having a multi-point connection for transferring data between a host unit and a plurality of terminal units, said backup apparatus comprising:

• an ISDN interface portion for transmitting and receiving a digital signal over an ISDN line;
• two A/D converting portions, referred to as a first A/D converting portions and a second A/D converting portion, each for receiving a first analog signal from a modem connected to said host unit, each for converting the first analog signal into a first digital signal synchronized with a timing of the ISDN line, and each for supplying the synchronized digital signal to said ISDN line through a respective channel in said ISDN interface portion;
• two D/A converting portions, referred to as a first D/A converting portion and a second D/A converting portion, each for receiving a third and fourth digital signal from said ISDN line through a respective channel in said ISDN interface portion, each for converting the third and fourth digital signal into a respective third and fourth analog signal, and each for supplying the third and fourth analog signal to said modem;
• a branching portion for receiving said first analog signal from said modem connected to said host unit and for supplying said first analog signal to an analog line connected between said host unit and said plurality of terminal units and to said first and second A/D converting portions;
• a compositing portion for supplying to said modem a second analog signal received from said analog line connected between said host unit and said plurality of terminal units and said third and fourth analog signals received from said first and second D/A converting portions;
• and
• a controller portion which controls said modem to connect with said analog line to transmit and receive data over said analog line when said analog line is functioning properly and which controls said ISDN interface portion to supply to said ISDN line from said host unit a channel data of digital signals which are received from said first and second A/D converting portions through said branching portion and to supply to said modem through said compositing portion two analog signals transmitted over said ISDN line from said plurality of terminal units and converted by said first and second D/A converting portions when a defect occurs over said analog line.

A backup method against a line defect for use in a communication system for performing communication over an analog line through a modem, said modem comprising a modulating portion for converting a digital signal into an analog signal and for supplying the analog signal and comprising a demodulating portion for converting an analog signal into a digital signal and for supplying the digital signal, said backup method comprising the steps of:

• transmitting and receiving a digital signal over an ISDN line, using an ISDN interface portion;
• receiving an analog signal from said modulating portion of said modem, converting the analog signal into a digital signal synchronized with a timing of the ISDN line, and supplying the synchronized digital signal to said ISDN line through said ISDN interface portion, using an A/D converting portion;
• receiving a digital signal from said ISDN line through said ISDN interface portion, converting the digital signal into a analog signal, and supplying the analog signal to said demodulating portion of said modem, using a D/A converting portion;
• and
• controlling the transmitting and receiving of data over said analog line when said analog line is functioning properly, and controlling the transmitting and receiving of data through said A/D converting portion, said D/A converting portion, and said ISDN interface portion over said ISDN line when a defect occurs in said analog line, using a controller portion.

A backup method against a line defect for use in a communication system having a multi-point connection for transferring data between a host unit and a plurality of terminal units through a modem via an analog line, said backup method comprising the steps of:

• transmitting and receiving a digital signal over an ISDN line, using an ISDN interface portion;
• using a first A/D converting portion and a second A/D converting portion each for receiving a first analog signal from said modem connected to said host unit, each for converting the first analog signal into a first digital signal synchronized with a timing of the ISDN line, and each for supplying the synchronized digital signal to said ISDN line through a respective channel in said ISDN interface portion;
• using a first D/A converting portion and a second D/A converting portion each for receiving a third and a fourth digital signal from said ISDN line through a respective channel in said ISDN interface portion, each for converting the third and fourth digital signal into a respective third and fourth analog signal, and each for supplying the analog signal to said modem;
• and
• controlling said modem to connect with said analog line for transmitting and receiving data over said analog line when said analog line is functioning properly and controlling said ISDN interface portion for transferring to said ISDN line from said host unit a channel data of digital signals which are received from said first and second A/D converting portions and for supplying to said modem two analog signals from data transmitted over said ISDN line from said plurality of terminal units and converted by first and second D/A converting portions when a defect occurs over said analog line, using a control portion.

A backup method against line defect for use in a communication system having a multi-point connection for transferring data between a host unit and a plurality of terminal units through a modem via an analog line, said backup method for comprising the steps of:

• (a) transmitting and receiving a digital signal over an ISDN line, using an ISDN interface portion;
• (b) using a first A/D converting portion and a second A/D convening portion, each for receiving a first analog signal from said modem connected to said host unit, each for converting the first analog signal into a first digital signal synchronized with a timing of the ISDN line, and each for supplying the synchronized digital signal to said ISDN line through a respective channel in said ISDN interface portion;
• (c) using a first D/A converting portion and a second D/A converting portion, each for receiving a third and fourth digital signal from said ISDN line through a respective channel in said ISDN interface portion, each for converting the third and fourth digital signal into a respective third and fourth analog signal, and each for supplying the third and fourth analog signal to said modem;
• (d) receiving said first analog signal from said modem connected to said host unit and supplying said first analog signal to an analog line connected between said host unit and said plurality of terminal units and to said first and second A/D converting portions, using a branching portion;
• (e) supplying to said modem a second analog signal received from said analog line connected between said host unit and said plurality of terminal units and said third and fourth analog signals received from said first and second D/A converting portions, using a compositing portion;
• and
• (f) controlling said modem connected with said analog line to transmit and receive data over said analog line when said analog line is functioning properly and controlling said ISDN interface portion to supply to said ISDN line from said host unit a channel data of digital signals which are received from said first and second A/D converting portions through said branching portion and to supply to said modem through said compositing portion two analog signals transmitted over said ISDN line from said plurality of terminal units and converted by said first and second D/A converting portions when a defect occurs over said analog line, using a controller portion.