单项选择题
A.1kHz正弦波调制,调制幅度80%B.2Hz正弦波调制,调制幅度80%C.方波调制,占空比50%,重复频率200HzD.方波调制,占空比1/8,重复频率217Hz
A.15.403B.15.407C.15.247D.15.209
A.EN300328B.EN301489-1/-17C.EN62479D.EN60950-1