对现代中央办公大楼的电讯设备可靠性一般都要求达到10~(-12)或更小的位误差率。而电源的性能好坏常常是信息传输质量的重要因素。电源电压通常额定为48V,有时也可增至60V。必须把电源电压控制在规定的范围内。通常标准的作法是,在把电力加给负载之前,自先监控干线电压的工作状态。如果工作状态令人满意,我们便可使用一个开关来给负载 The reliability of telecommunications equipment in modern central office buildings generally requires a bit error rate of 10 ~ (-12) or less. The performance of the power supply is often an important factor in the quality of information transmission. The supply voltage is usually rated at 48V, sometimes up to 60V. The power supply voltage must be controlled within the specified range. It is generally standard practice to monitor the mains voltage before it is applied to the load. If the working condition is satisfactory, we can use a switch to load