| 摘要 |
PROBLEM TO BE SOLVED: To avoid giving unpleasant feelings caused by noise at the rise and fall of a charging pulse from applied to the user of telephone terminal equipment, such as a public telephone connected to a subscriber device for WLL by gradually increasing the amplitude of the charging pulse to be transmitted, when starting the transmission of the charging pulse, and gradually decreasing the amplitude toward ending the transmission. SOLUTION: The charging information reporting part of the subscriber device switches resistors Ra, Rb, Rc and Rd connected between the output terminal and noninverted input terminal of an operational amplifier OP by operating a noise reduction circuit 273 to be controlled by a control part, adjusts the output level of the charging pulse step by step, prevents disconnection, so as not to rapidly output the charging pulse with a large peak value or not to rapidly turn the charging pulse from the peak value into zero level and finally turn the pulse into peak value by increasing the level gradually from a lower peak value with a fade-in operation and at cutoff, cutoff is performed in reverse to this by gradually decreasing the level from the peak value with a fade-out operation.
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