| 摘要 |
PURPOSE:To simplify the processing steps of howler trip of a central processing device, by providing a loop circuit connected to switching elements leading channels of subscriber lines and switching the loop circuit in response to the switching state of subscriber terminal loops derected at a subscriber loop detection circuit. CONSTITUTION:A howler tone detection circuit HOW is connected to a subscriber loop detection circuit LD2 and the loop circuit LOP consisting of a photocoupler PH activated with the circuit LD2 and a resistor R is connected. The circuits HOW and LD2 are connected to a switching contact rl of a relay RL at the subscriber terminal of a subscriber circuit LC and a contact rl at the circuit LC is connected with the circuit LOP. The central controller CC is provided with a subscriber monitor section LCD and a subscriber memory LM. A signal of a subscriber terminal SUB is detected at a subscriber loop detection circuit LD1 and subscriber loop information is applied to the LCD of the controller CC via a signal highway SHW, allowing to simplify the processing steps of the howler trip of the controller CC. |
