This kind of control equipment mostly appears in the fire fighting lines. The common way is two-way power supply. One way is normal line power supply, the other way may be standby power supply from another transformer, or it may be power supply from diesel generator. When the power of external network is cut off, the standby power supply can be quickly started to ensure that the fire fighting is always in operation, When a fire accident occurs, it can be started in time, so how to install the dual power line, there are two options, one is the contactor controlled dual power switch, this switch is low cost, only suitable for ordinary equipment.

还有一种是双电源转换开关，它是供电气设备使用的双电源切换开关；接触器组成的双电源开关，用电时合上两个空开断路器，KM1得电吸合，甲常用电源闭合得电向负载供电，由于KM1吸合，乙电源的KM1常闭触点弹开关闭电源。如果甲电源停止供电，那么乙电源的KM1处常闭点接通电源，时间继电器工作使常开触点闭合，使KM2得电吸合并自锁，乙电源向负载供电，乙电源正常供电。

There is also a dual power switch, which is used for electrical equipment dual power switch; The double power switch composed of contactors, when using electricity, closes two air switch circuit breakers, KM1 is powered on and closed, and the common power supply of Party A is closed to supply power to the load. Because KM1 is closed, the normally closed contact of Party B's KM1 is opened and closed. If the power supply of Party A stops, the normally closed point of KM1 of Party B is connected to the power supply, and the time relay works to close the normally open contact, so that km2 is powered on and self locked, Party B supplies power to the load, and Party B supplies power normally.

双电源转换开关，它是原理是：可以在常用电源和备用电源之间进行自动转换的开关。它是由一个或多个转换开关电器和其他必要的电器组成，用来检测电路，并且当常用电源出现故障时，通过双电源自动转换开关，自动将负载转换到备用电源上，使用电设备能正常运行。

Dual power transfer switch, its principle is: can be in common power supply and standby power supply between automatic transfer switch. It is composed of one or more transfer switch electrical appliances and other necessary electrical appliances, used to detect the circuit, and when the common power failure, through the dual power automatic transfer switch, automatically transfer the load to the standby power supply, the use of electrical equipment can operate normally.

是一种安全可靠、自动化的、使用范围越来越广泛的电气这种双电源切换开关接线简单，深受消防控制设备安装人员的喜爱。在消防方面得到了良好的应用，使用也越来越广泛，比如监控设施。

It is a safe, reliable, automatic, more and more widely used electrical equipment. This dual power switch has simple wiring and is deeply loved by the fire control equipment installation personnel. It has been widely used in fire protection, such as monitoring facilities.