| 摘要 |
A digital-transmission/analog-transmission changeover apparatus in a communication system for performing a digital transmission between a digital terminal and a terminal accommodated by an ISDN, and performing an analog transmission via the ISDN and an analog network, between the digital terminal and a terminal accommodated by the analog network includes a rate converter for converting the rate of data, which has entered from the digital terminal, to a rate suited to the ISDN, and for converting the rate of data, which has entered from the ISDN, to the rate of the digital terminal. A modulator/demodulator for modulating digital data, which has entered from the digital terminal, into an analog signal and demodulating the analog signal into digital data is provided. A PCM converter is connected to the modulator/demodulator for converting the analog signal into digital data at a rate suited to the ISDN, and converting digital data from the ISDN into the analog signal. An ISDN communication controller is connected to the rate converter and the PCM converter for performing communication control in accordance with an ISDN protocol. A connection controller connects the digital terminal either to the rate converter or to the modulator/demodulator.
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