Possess modular structure, allow subscriber to upgrade system capacity.

积木结构，可满足用户日后系统扩容需求。

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ADSL is one of the modulation techniques. Using the wideband capacity in copper twisted-pair cable, high speed data can be transmitted on the subscriber line.

ADSL技术是一种调制技术，在双绞铜线的两端分别接入adsl调制解调器，即可利用其高频宽带特性传送高速数据。

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Unicom has struggled, signing up only 30 million CDMA customers--well below its capacity of 70 million--a subscriber base only a sixth the size of that of China Mobile, the dominant GSM carrier.

FORBES