Importance

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Abstract

Conventional telephone systems including terminal equipments interconnected by a communications channel typically employ a supervisory tone transmitted by each terminal equipment to indicate its idle condition. Because the fraction of idle terminal equipments may be high, the total energy carried over the channel is substantially determined by these tones. The apparatus of the type disclosed herein, employed in association with each terminal equipment, effects a reduction in the channel power loading due to those tones. The apparatus includes circuits for detecting the presence of the idle state supervisory tone being transmitted from or received by the associated terminal. If the tone is present on either the transmit or received lead, the signal transmitted by the terminal into the channel is attenuated by a fixed power ratio and the signal received by the terminal from the channel is amplified by the same fixed power ratio.

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First Claim