| 摘要 |
A projector comprises: a cooling fan for sucking ambient air through a filter; switching means for switching the operational mode of the cooling fan between a lowland mode and a highland mode; and control means adapted to obtain current fan voltage to determine the normal rpm value for that current fan voltage in reference to a highland voltage-rpm characteristic when the switching means is in the highland mode, obtain current fan rpm, and enables alarming means to issue a filter clogging alarm in the event that the current fan rpm is larger than the normal rpm value plus a predetermined value. Thus, filter clogging can be detected with precision in highlands.
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