Unfortunately, limited by the characteristic of real telephone channels, it has not completely solved the full-duplex difficulty problem up to now.

不幸的是，由于受实际电话信道特性的影响，该技术至今尚未完全解决这一全双工难题。

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The echo cancellation technique is now widely used to implement the full-duplex communication in almost all telephone privacy systems.

几乎所有的电话保密系统都使用回波抵消技术来实现全双工通信。

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Between the center and the devices, the duplex communication links are created through the public switched telephone network, thus the remote management for the devices is realized.

集中管理中心与集中管理式电话计费器之间可通过公众电话网以拨号方式建立双向通信链路，从而实现对集中管理式电话计费器的远程管理。

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