| 摘要 |
<p>PURPOSE:To eliminate a high voltage signal and to obtain a system suitable to the integrated circuit technology, by interrupting the loop of a subscriber line to both polarities or one polarity, in a response display of an exchange. CONSTITUTION:While the user recognizes the generation of a terminal calling signal RNGT and a response signal OHK is generated or the polarity is inverted to the normal polarity of a line current, a terminal device TERM generates a terminal calling signal RNGT. When the user responds and generates the response signal OHK, a calling control circuit RCT generates a response interruption control signal SOF, drives a response interruption switch SHOT, hits the line current flowing to the subscriber line, and displays the response to an exchange. The response of the line current is monitored at the exchange and the response of the terminal device is recognized. To explain by an example concretely, the presence of the line current is detected at line current supply circuit BS of a subscriber circuit SLC, the controller monitors the result of detection periodically and detects the hit of the line current.</p> |
