| 摘要 |
An electronic digital thermostat adapted for installation in locations with or without an external power supply preferably includes a compartment for receiving a replaceable internal power supply, such as a batteries, for powering the thermostat if an external power supply is not available, and a connector for connecting the thermostat to an external power supply for powering the thermostat when the external power supply is available. The thermostat is configured to preferentially draw power from an external power supply connected to the thermostat, if power from an external power supply is available, and draw power from an internal power supply connected to the thermostat, if power from an external power supply is not available. An additional power backup, such as a capacitor, may be provided to maintain power to the thermostat for short durations when power is unavailable from both the internal power supply and the external power supply.
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