audio-frequency electric amplifiers的意思|示意

耳机 ...耳机、耳塞机，不论是否装有传声器，由传声器及一个或多个扬声器组成的组合机；音频扩大器；电气扩音机组:Microphones and stands therefor; loudspeakers, whether or not mounted in their enclosures; headphones earphones, whether or not combined with a microphone, and sets consisting of a microphone and one or more loudspeakers; audio-frequency electric amplifiers;electric sound amplifier sets: 声音录制或重放设备: Sound recording or reproducing apparatus: ..