| 摘要 |
PURPOSE: A telephone set connected by the electronic dial tone of a portable phone is provided to offer an auxiliary telephone so as to use a portable phone as a wire telephone. CONSTITUTION: An auxiliary telephone(15) in a portable phone(12) includes an input/output extension cable(3), a phone plug(2), and a high sensitive microphone(1). The input/output extension cable(3) is provided to receive the electronic dial tone of the portable phone(12). The phone plug(2) accepts the jack of an earphone(4). The auxiliary telephone(15) also comprises a filter(10), an automatic gain control circuit part(11), a transmit/receive signal amplification part(5), and a ring oscillation part(9). The filter(10) filters the frequency of a signal received to the microphone(1). The automatic gain control circuit part(11) controls the signal of the filtered frequency to an optimum level. The transmit/receive signal amplification part(5) amplifies the signal outputted from the automatic gain control circuit part(11). The ring oscillation part(9), connected to a buzzer(8), detects a 20-60Hz signal sound supplied through a wired telephone network(13) and rings the buzzer(8).
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