| 摘要 |
PURPOSE:To decide quickly a line fault by detecting the disconnection of an outgoing line due to out of clock synchronization in a transmitter/receiver at the subscriber side and detecting the level of a pilot signal by a transmitter/ receiver of the supervisory station side to use a simple circuit to send the information of the disconnection of the outgoing line to a supervisory station. CONSTITUTION:A frequency modulation (FSK) wave sent from a subscriber side is inputted as a data signal to a line terminator 4. When the outgoing line is faulty, a non-modulation wave sent as a pilot signal through an incoming line from the subscriber side in the figure is detected by circuits 28-30. That is, a reception IF output of a frequency conversion section 28 at the non- modulation due to the outgoing line disconnection (fault) has a higher level than that with the modulation at the normal line, the signal passes at first through a band pass filter 29, the result is detected by a level detection section 30. Then the disconnection of the outgoing line is decided and the information representing the outgoing line disconnection is sent to the line terminator 4 at the supervisory station side supervise the line. |
