| 摘要 |
One of a plurality of subscribers connecting via a communications line a signal line and switching units, each accommodating a subscriber line connected to a terminal, etc., lowers the communication quality of the communications to reduce the cost of communications. A calling or called subscriber issues to a switching unit an instruction to lower the communication quality. A control unit in one of the switching unit receives the instruction, analyzes a method of lowering the communication quality and determining a switching unit for performing it, generates a control signal indicating that the communication quality should be lowered, and sends via a signal line the control signal to the switching unit determined to be used for lowering the communication quality. After receiving the control signal, a polishing unit in that switching unit lowers the communication quality by discarding a part of communication contents of the communications according to the control signal, or lowering the priority of the communication contents. Thus, communications fees can be greatly reduced.
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