| 摘要 |
The box (1) has a probe (2) connected for measurement of the external temperature and provides an output for electric heating elements (3) which may be placed near to the plants to be protected. When the temperature falls, the heating elements are switched on, but are regulated to be kept below a maximum heating temperature. The equipment includes a box (1) which has a probe (2) connected for measurement of the external temperature. This may be a physical connection, or the connection may be provided by a radio link. The box may be mounted indoors and connected to the mains supply. The box provides an output for electric heating elements (3) which may be placed near to the plants to be protected. When the temperature falls, the heating elements are switched on, but the heating level is determined by the measured temperature, with reference to a reference temperature, and a maximum heating temperature. Heating is achieved using an electric cable having a metal conducting core situated inside a sleeve which is resistant to UV and resistant to corrosion. This may comprise a nickel-chrome resistance wire which is double-insulated in a silicon material.
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