polarityn.极性；磁性引力；两极polarity of feedback loop反馈环的极性polarity of feedback link反馈链的极性polarity telegraph system极性电报制polarity directional relay极化方向继电器polarity of picture signal[电] 图像讯号的极性polarity of electric field电场极性polarity-reversing switch极性转换开关polarity inverting amplifier极性反转放大器,倒相放大器polarity-directional relay极化继电器polarity separation technique极性分离技术