| 摘要 |
PURPOSE:To reduce the number of components by connecting a choke coil in series with a power line and an earth line of a DCIN jack and utilizing the difference in the impedance of a plug inserted to the DCIN jack so as to control electrically the connection of a battery built in a device into the main body circuit. CONSTITUTION:With power switches 7,9 in the operating state, that is, with the power switch 7 thrown between terminals a-c, and with the power switch 9 thrown between terminals b-d, a transistor (TR) 5 is turned off, a TR 8 is turned on, a buil-in battery 10 is connected to a power output terminal 1 via the TR 8 to supply power to the main body circuit. On the other hand, in plugging an AC adpator into the DCIN jack 11, the lead of the AC adaptor acts like an FM antenna, a power terminal (g) of the DCIN jack 11 and a switch terminal (h) are separated, the TR 5 is turned on, the TR 8 is turned off, and the power of the AC adaptor appears at the power output terminal 1 via the TR 5 to supply the power to the main body circuit.
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