| 摘要 |
PROBLEM TO BE SOLVED: To provide an information terminal and an information terminal system, where an extension call can be made with other information terminal during an external call. SOLUTION: A modulation circuit 5 modulates a voice signal picked up by a microphone 7, to have a voice signal frequency band 18 shown in Figure 2 and the modulated signal is sent to an exchange station via an LPF 26, a transformer 25 and a subscriber line A. Conversely a voice signal, sent from the exchange station via the subscriber line A is received by a demodulation circuit 6 via the transformer 25 and the LPF 26, which extracts required signal components and demodulates the signal to have a conventional voice frequency band, and the demodulated signal is sounded from a loudspeaker 8. Then in the case of making an extension call, the voice signal received from the microphone 7 is converted into a digital signal, that is assembled into packets by a telephone line interface circuit 28, the signal is modulated to have a frequency band 21 and transmitted via the transformer 25 and a private telephone line 17.
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