华为系统中,下面关于CBTS基站防雷设计的说法,正确的是()
A. 对于450/800MHz频段,基站的天馈部分和CDU(或DFDDU)单元内部直流接地,天馈感应的雷电流可以直接通过短接点泄放到地,无需外置避雷器即可达到防护要求
B. 基站中继线防雷设计都是在机顶防雷板(BESP)中实现的。
C. 对于450/800/1900MHz频段,都需要外置天馈避雷器才可达到防护要求。
D. GPS/GLONASS天馈防雷,通常情况下要在天线侧和机柜设备侧各串接一个避雷器,以防止馈线芯线感应的雷电电流对设备和天线造成损害。
mary would like to display a collapsed section on her video catalog form, she has created a section buy when she display the form in the client the section always opens expanded. which one of the following should mary do to collapse the section?()
A. nothing. Sections always open expanded
B. modify the section default properties to collapsed
C. modify the form propenties to display all sections collapsed
D. modify the section opened for reading property to auto-collapse&e