Each stage of converting and transmitting power results in a loss of efficiency, but with technological improvements these losses are being reduced.

在电力转换和传送的各个阶段都会伴随效率的损失，但是随着科技的进步这些效率的损失正逐步减少。

A telephone wire, however, loses much of its transmitting power when placed under ground, and it took many years of experimenting before the engineers perfected these subways.

然而，电话线在地下时会损失大部分传输功率， 工程师们经过多年的试验才完善了这些地铁。