| 摘要 |
PURPOSE:To easily offer sound volume control services to a subscriber as well with a popular telephone set by moving a sound volume control function to a subscriber circuit in an exchange from a subscriber terminal. CONSTITUTION:The subscriber circuit LC 2 and an in-house popular telephone set TEL 1 are connected through a two-line cable 6. The LC 2 is provided with a balancing network supervisory hybrid circuit BSH 3, a sound volume control circuit part 13 and a cordic circuit COD 5. It converts a reception PCM signal 14 into a reception analog signal 10 which turns out to be the four-line side input 11 of the BSH 3 after a level converter circuit LCV 4 converts the level of the signal. The sound volume control circuit part 13 is composed of a numeric reception circuit DGR 8, a CTL 9 and the LCV 4. After the DGR 8 numeric-recognizes dial pulse information transmitted from the TEL 1 during calling with the aid of a supervisory signal 7 outputted from the BSH 3, said information is transmitted to the CTL 9. It controls the LCV 4 so that a preset corresponding value can be attained with the aid of the output signal of the DGR 8.
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