| 摘要 |
PURPOSE:To cancel an inductive voltage of a telephone terminal set, and to suppress inductive noise of a subscriber line connecting lots of telephone sets with a simple constitution, by installing an auxiliary line along each subscriber line and applying a signal having an opposite phase with a high frequency component interfering with the auxiliary line. CONSTITUTION:A main device 1 of a key telephone set and plural telephone sets 2 are connected via plural subscriber lines 3 and plural communication lines 4 are connected to the main device 1. An auxiliary line 5 is installed along the subscriber line 3 and a high frequency filter 6 is connected to one of communication lines 4. The inductive components are extracted from the lines 4 at the filter 6, the components are applied to a phase inverting circuit 7, and they are extracted as an opposite phase signal. After an output voltage is adjusted at a level adjusting device 8, the voltage is applied to each auxiliary line 5, the high frequency components of the opposite phase are induced in the subscriber line 3, allowing to cancel the interference noise induced in the subscriber line 3. |
