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。
2
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。
3
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.