?话音级调变解调器

... voice-grade lines 话音级线路 voice-grade modems 话音级调变解调器 voice-grade service(voice channel) 话音级服务(音频通道) ...

?话音级线路

... 话音级通道 voice-grade lines 话音级线路 voice-grade modems 话音级服务(音频通道) voice-over ...