| 摘要 |
PURPOSE:To attain a call with an optimum sound volume at all times, by discriminating an opposite telephone set whether the set is analog or digital type at the start of a telephone call, and varying the gain of an amplifier for transmission/reception according to the ability of discrimination. CONSTITUTION:A generating circuit 7 for a terminal code signal generates a terminal code representing a digital type telephone set and the code signal is discriminated at a terminal code signal reception circuit 6. At the start of telephone call, whether an opposite telephone set is a digital or an analog type telephone set is discriminated at the circuit 6 with the transmission/reception of the terminal code signal. As a result, when the telephone set is the digital telephone set, the gain of a reception amplifier 4 is controlled at a gain control circuit 8 to make it equal to the sound volume of the analog type telephone set. |
