| 摘要 |
A communication line adapter to enable simultaneous communication with the main controller and a plurality of terminals comprising an interface controller for interfacing digital command and data between the main controller and the public telephone network; a HDLC controller connected between the main controller and the interface controller for interfacing packeted digital command and data between the main controller and the interface controller in response to a periodic call of the main controller; a modem connected between the interface controller and the public telephone network for modulating to analog signal the digital data to be transmitted from the interface controller to the public telephone network and demodulating analog signal supplied from the public telephone network to digital command and data to be transmitted to the interface controller; a serial controller connected between the modem and the interface controller for converting into serial type, digital command and data to be transmitted from the interface controller to the modem, and converting into parallel type, serial digital command and data to be transmitted from the modem to the interface controller; a DTMF transmitter for encoding a phone number supplied from the interface controller to a DTMF signal and transmitting the encoded DTMF signal to the public telephone network; and a ring detector for detecting a ring signal from the public telephone network to supply the detected ring signal to the interface controller, whereby independently communicating with the main controller and a terminal connected to the public telephone network.
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