| 摘要 |
PROBLEM TO BE SOLVED: To provide an in-band ringer for achieving dial-in connection to a telephone being accommodated in a PBX using an exclusive line from a switchboard. SOLUTION: This in-band ringer is composed by connecting the switchboard 9 having an OD trunk, a PBX 10 having a CO trunk, an in-band ringer 11 for OD trunks for inputting and outputting by converting a controls to a plurality of control signals composed by an in-band frequency, or by converting the plurality of control signals composed by an in-band frequency to the control signal, an in-band ringer 12 for CO trunks for inputting or outputting by converting the control signal to the plurality of control signal composed by an in-band frequency, or by converting the plurality of control signals composed by an in-band frequency to the control signal while the in-band ringer 12 has the polarity inversion section of a DC application voltage, and a plurality of telephones 13a, 13b, and 13c accommodated in the PBX 10.
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