| 摘要 |
A PABX is provided to supply voltage of a sufficient level, thereby satisfying power request conditions to operate a digital keyset normally which is installed in a remote place. A PABX(Private Automatic Branch eXchange) comprises a keyset interface, a controller(144), a switching unit(146) and a system main power unit. The keyset interface is connected with digital keysets through an extension, and supplies voltage of a selected level to the digital keysets through the extension. Voltage of the selected level is attenuated through the extension, and sufficiently big so as to be threshold voltage or more when being transmitted to an input terminal of the digital keysets. The system main power unit is a power circuit to supply power to the keyset interface, controller, and switching unit within the PABX by being connected(148a, 148b, 148c) with the keyset interface, controller, and switching unit.
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