It is important that Series 774 be tested periodically in compliance with local codes, but at least once a year or more often, depending upon system conditions.是什么意思_It is important that Series 774 be tested periodically in compliance with local codes, but at least once a year or more often, depending upon system conditions.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句