| 摘要 |
PROBLEM TO BE SOLVED: To prolong the lifetime of a battery by reducing loss. SOLUTION: A relay 20 has an ON terminal being supplied with a power supply voltage from a terminal 16 connected with the positive polarity end of an AC adapter 3 and an OFF terminal being supplied with a power supply voltage from a terminal 19 connected with the positive polarity end of a battery 21. An input voltage decision circuit 25 generates an ON signal when the AC adapter 3 is connected and generates an OFF signal when the AC adapter 3 is removed. When the AC adapter 3 is connected, the relay 20 selects a power supply input from the AC adapter 3 preferentially in response to an ON signal from the input voltage decision circuit 25. Since no diode is employed in the selection of power supply input and no element causing a voltage drop is present in the current path to a thermal head, lifetime of the battery can be prolonged.
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