ISDN is used on digital lines as well as on voice-grade lines.
整合服务数位网路在数位线路上被使用就如同在声音等级的线路上。
2
Some people say the voice is their father’s or grandmother’s or the voice of their third-grade teacher.
一些人说这想法是他们父亲的，或是他们祖母的，或是他们三年级老师的。
3
A data channel on which the information transmitted can take any value between the limits defined by the channel. Voice - grade channels are analog channels.