PRIVATE BRANCH EXCHANGE, TELEPHONE TERMINAL, AND TELEPHONE SYSTEM HAVING THE PRIVATE BRANCH EXCHANGE AND THE TELEPHONE TERMINAL
A PBX transmits a superimposed signal to telephones via internal lines, the signal being generated from a transmission data signal modulated and converted into an analog form and a transmission voice signal. The PBX also receives a superimposed signal from the telephones via the internal lines, the signal being generated from a reception data signal and a reception voice signal. The PBX then retrieves the reception data signal and the reception voice signal separately, and digitally converts and modulates the reception data signal. The telephones also have similar functions as those of the PBX and communicate with the PBX via the internal lines.
1 . A private branch exchange that is connected to a public telephone network, a data communication network and an internal line, the internal line connecting to a telephone terminal, the private branch exchange comprising:
a modulator that modulates a first digital data signal and that outputs a first modulated digital data signal;
an analog converter that converts the first modulated digital data signal into a first analog data signal;
a transmitter that superimposes the first analog data signal on a first sound data signal and that transmits a first superimposed signal to the telephone terminal via the internal line, the first sound data signal being received from the public telephone network;
a receiver that receives a second superimposed signal from the telephone terminal via the internal line and that extracts a second analog data signal from the second superimposed signal;
a digital converter that converts the second analog data signal into a second modulated digital data signal; and
a demodulator that demodulates the second modulated digital data signal and that outputs a second digital data signal.
2 . The private branch exchange according to claim 1 , wherein the receiver extracts a second sound data signal from the second superimposed signal, the second sound data signal being output to the public telephone network.
3 . The private branch exchange according to claim 1 further comprising a power line communication controller, the second digital data signal being output to a power line via the power line controller.
4 . A telephone terminal that is connected to a private branch exchange via an internal line and to a data communication network, the telephone terminal comprising:
a connector configured to input an input sound data signal;
a modulator that modulates a third digital data signal and that outputs a third modulated digital data signal;
an analog converter that converts the third modulated digital data signal into a third analog data signal;
a transmitter that superimposes the third analog data signal on the input sound data signal and that transmits a third superimposed signal to the private branch exchange via the internal line;
a receiver that receives a fourth superimposed signal from the private branch exchange via the internal line and that extracts a fourth analog data signal from the fourth superimposed signal;
a digital converter that converts the fourth analog data signal into a fourth modulated digital signal; and
a demodulator that demodulates the fourth modulated digital data signal and that outputs a fourth digital data signal.
5 . The telephone terminal according to claim 4 , wherein the receiver extracts an output sound data signal from the fourth superimposed signal, the output sound data signal being output via the connector.
6 . A telephone system comprising a private branch exchange and a telephone terminal, the private branch exchange being connected to a public telephone network, a data communication network and a internal line, the telephone terminal being connected to the internal line,
wherein the private branch exchange comprises:
a first modulator that modulates a first digital data signal and that outputs a first modulated digital data signal;
a first analog converter that converts the first modulated digital data signal into a first analog data signal;
a first transmitter that superimposes the first analog data signal on a first sound data signal and that transmits a first superimposed signal to the telephone terminal via the internal line, the first sound data signal being received from the public telephone network;
a first receiver that receives a second superimposed signal from the telephone terminal via the internal line and that extracts a second analog data signal from the second superimposed signal;
a first digital converter that converts the second analog data signal into a second modulated digital data signal; and
a first demodulator that demodulates the second modulated digital data signal and that outputs a second digital data signal, and
wherein the telephone terminal:
a connector configured to input an input sound data signal;
a second modulator that modulates a third digital data signal and that outputs a third modulated digital data signal;
a second analog converter that converts the third modulated digital data signal into a third analog data signal;
a second transmitter that superimposes the third analog data signal on the input sound data signal and that transmits a third superimposed signal to the private branch exchange via the internal line;
a second receiver that receives a fourth superimposed signal from the private branch exchange via the internal line and that extracts a fourth analog data signal from the fourth superimposed signal;
a second digital converter that converts the fourth analog data signal into a fourth modulated digital signal; and
a second demodulator that demodulates the fourth modulated digital data signal and that outputs a fourth digital data signal.