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徒弟:有一台HA18P/T型电话机,通话正常,脉冲拨号也正常,但双音频拨号失效,该如何检修? 师傅:该机可做如下三个步骤的检修: 1.如图所示,该机的拨号集成块 IN_3(DCD3310AP)的第②脚接有发号制式转换开关SA_2, 当开关置“P”位时,②脚输入为V_(53),内部系统被设定为脉冲发号,置“T”位时,②脚输入为V_(DD),内部系统被设定为双音频发号。因此出现该故障时,可先检查“P”/“T”选择开关是否在“T”位,如开关位置正确,可进一步检查IN_3第②脚电压是否为V_(DD),如果②
Apprentice: There is a HA18P / T telephone, the call is normal, pulse dialing is normal, but the dual tone dial-up failure, how to repair? Master: The aircraft can do the following three steps for maintenance: 1. As shown, the When the switch is set to “P”, ② pin input is V_ (53), the internal system is set to pulse number, When set to “T”, ② pin input is V_ (DD), the internal system is set to dual audio frequency. Therefore, when the fault occurs, first check whether the “P” / “T” selector switch is in the “T” position. If the switch is in the correct position, check if the voltage in the second leg of IN_3 is V_ (DD)