单项选择题
A.A机和B机同时接受值班员命令 B.B机接受值班员命令,A机不接受 C.A机接受值班员命令,B机不接受
A.4.75-5.25VDC B.4.75-5.25VAC C.3.75-4.25VDC D.3.75-4.25VAC
A.5 B.6 C.7 D.8