| 摘要 |
PURPOSE:To prevent mixing of noise to data communication service attended with connection by allowing a common controller to detect a middle potential of a talking line of an incoming subscriber at the incoming connection to a subscriber and deciding the propriety of interruption connection from the result. CONSTITUTION:When the common controller M draws a talking line of a subscriber SUB to a resistor RH and the line is during connection with a trunk TRKA, an intermediate voltage, e.g., VH=-24V is detected. Then the voltage VH represents nearly a half of a power supply -48V of a relay A independently of the subscriber resistance or the like. As a result, no VOUT output is given from a comparator IC because the intermediate voltage VH is lower than a reference potential VS=-12V, and the controller M applies interruption connection. While the subscriber SUB is connected to a trunk TRKB, the intermediate potential VH reaches OV. Thus, the comparator IC outputs the VOUT because the VH is higher than the potential VS=-12V, then it is detected that the controller M is connected to a data line and no interruption connection is applied. |
