hoho~ 老大糊涂了吧？ ^-^

Half-duplex sound cards are only capable of either recording or playing. Full-duplex sound cards allow simultaneous recording and playback.

Full-duplex不就是双工声卡吗？
simultaneous recording and playback 就是能在聊天室中放音乐和唱歌，即卡拉OK

http://www.newsearching.com/sound_card/sound_card.html