| 摘要 |
Undesired noise signals associated with the battery utilized in a telephone battery feed circuit are minimized. In one embodiment, the noise voltage is amplified and inverted in phase and added back to a location on the ring line in order to provide substantial cancellation of the original noise voltage which would have appeared at the same location. In another embodiment, the noise voltage coupled to the ring line is reproduced as a replica signal. The replica signal is added in series with the tip line so as to provide equal phase and magnitude relationships relative to earth ground, thereby effectively canceling the noise current which would have flowed from the original noise source.
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