传统的固定电话网是由()三部分组成。

A、交换设备,传输设备和用户电路
B、交换设备,传输设备和用户终端设备
C、交换设备,用户电缆和信令设备
D、信令设备,传输设备和用户电路
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正确答案:

B

答案解析:

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