US Patent 7574730 Device and system for reducing confluence noise

A system for reducing noise in a signal line, through which upward signals and downward signals are transmitted between a center and terminals, includes a noise-reduction device provided between the center and the terminals. The noise-reduction device attenuates the upward signals by an increased amount when a noise increase regarding the upward signals is detected on the signal line. The system further includes a noise-control device, provided at terminals, which boosts a transmission level of the upward signals by an amount compensating for the attenuation of the upward signals by the noise-reduction device.