Voicefrequencyequipment: input, outputamplifier,compensatingcapacitor,the voicefrequencyamplifier,preamplifier,poweramplifieretc.. Powersupplyequipment: seriesvoltageregulation,switchmodulator,andDC-ACtransducer...etc.. Telecommunicationelectronequipment: highfrequencyamplifier,filtertelephone,se...